diff --git a/background.js b/background.js
index 3b4bbf1b0d41eaa178c105f03302f22ac2554ae2..722f58204398606977ed7a10f5c165b0bd606ee0 100644
--- a/background.js
+++ b/background.js
@@ -10,53 +10,47 @@
 
 "use strict";
 
-var config ;
-var started = "off";
-var debug_mode = false;
+let config ;
+let started = "off";
+let debug_mode = false;
 
 // if configuration exist 
-if (localStorage.getItem('config'))  
-	{
-	console.log("Load standard config");
-	config= JSON.parse(localStorage.getItem('config'));
-	
-	// If config 1.0 (Simple Modify headers V1.2) , save to format 1.1	
-	if (config.format_version=="1.0") 
-		{
-		config.format_version="1.1";
-		for (var line of config.headers) line.apply_on="req";
-		config.debug_mode=false;
-		console.log("save new config"+JSON.stringify(config));
-		localStorage.setItem("config",JSON.stringify(config));
-		}
-	}
-else 
-	{
-	// else check if old config exist (Simple Modify headers V1.1)
-	if (localStorage.getItem('targetPage')&& localStorage.getItem('modifyTable'))
-		{
-			console.log("Load old config");
-			var headers = [];
-			var modifyTable=JSON.parse(localStorage.getItem("modifyTable"));
-			for (var to_modify of modifyTable)
-				{
-					headers.push({action:to_modify[0],header_name:to_modify[1],header_value:to_modify[2],comment:"",apply_on:"req",status:to_modify[3]});
-				}
-			config = {format_version:"1.1",target_page:localStorage.getItem('targetPage'),headers:headers,debug_mode:false};
-			// save old config in new format 
-			localStorage.setItem("config",JSON.stringify(config));
-		}
-	//else no config exists, create a default one
-	else 
-		{
-				console.log("Load default config");
-				var headers = [];
-				headers.push({action:"add",header_name:"test-header-name",header_value:"test-header-value",comment:"test",apply_on:"req",status:"on"});
-				config = {format_version:"1.1",target_page:"https://httpbin.org/*",headers:headers,debug_mode:false};
-				// save configuration 
-				localStorage.setItem("config",JSON.stringify(config));
-		}
-	}
+if (localStorage.getItem('config')) {
+  console.log("Load standard config");
+  config= JSON.parse(localStorage.getItem('config'));	
+  
+ // If config 1.0 (Simple Modify headers V1.2) , save to format 1.1	
+  if (config.format_version==="1.0") {
+    config.format_version="1.1";
+    for (let line of config.headers) line.apply_on="req";
+    config.debug_mode=false;
+    console.log("save new config"+JSON.stringify(config));
+    localStorage.setItem("config",JSON.stringify(config));
+  }
+}
+else {
+  // else check if old config exist (Simple Modify headers V1.1)
+  if (localStorage.getItem('targetPage')&& localStorage.getItem('modifyTable')) {
+    console.log("Load old config");
+    let headers = [];
+    let modifyTable=JSON.parse(localStorage.getItem("modifyTable"));
+    for (const to_modify of modifyTable) {
+      headers.push({action:to_modify[0],header_name:to_modify[1],header_value:to_modify[2],comment:"",apply_on:"req",status:to_modify[3]});
+    }
+    config = {format_version:"1.1",target_page:localStorage.getItem('targetPage'),headers:headers,debug_mode:false};
+    // save old config in new format 
+    localStorage.setItem("config",JSON.stringify(config));
+  }
+  //else no config exists, create a default one
+  else {
+    console.log("Load default config");
+    let headers = [];
+    headers.push({action:"add",header_name:"test-header-name",header_value:"test-header-value",comment:"test",apply_on:"req",status:"on"});
+    config = {format_version:"1.1",target_page:"https://httpbin.org/*",headers:headers,debug_mode:false};
+    // save configuration 
+    localStorage.setItem("config",JSON.stringify(config));
+  }
+}
 		
 		
 // If no started value stored , use a default one 
@@ -64,11 +58,10 @@ if (!localStorage.getItem('started')) localStorage.setItem('started',started);
 else started = localStorage.getItem('started');
 
 
-if (started=="on") 
-		{
-		addListener();
-		browser.browserAction.setIcon({ path: "icons/modify-green-32.png"});
-		}
+if (started==="on") {
+  addListener();
+  browser.browserAction.setIcon({ path: "icons/modify-green-32.png"});
+}
 
 // listen for change in configuration or start/stop 
 browser.runtime.onMessage.addListener(notify);
@@ -79,55 +72,43 @@ browser.runtime.onMessage.addListener(notify);
 *
 */
 
-function log(message)
-{
-console.log(new Date() + " SimpleModifyHeader : " + message);
+function log(message) {
+  console.log(new Date() + " SimpleModifyHeader : " + message);
 }
 
 /*
 * Rewrite the request header (add , modify or delete)
 *
 */
-function rewriteRequestHeader(e) 
-{
+function rewriteRequestHeader(e) {
   if (config.debug_mode) log("Start modify request headers for url " + e.url);
-  for (var to_modify of config.headers)
-	{
-		if ((to_modify.status=="on")&&(to_modify.apply_on=="req"))
-			{
-			if (to_modify.action=="add")  
-				{
-					var new_header = {"name" :to_modify.header_name,"value":to_modify.header_value};
-					e.requestHeaders.push(new_header);
-					if (config.debug_mode) log("Add request header : name=" + to_modify.header_name + ",value=" + to_modify.header_value + " for url " + e.url);
-				}
-			else if (to_modify.action=="modify")
-				{
-				for (var header of e.requestHeaders) 
-					{
-					if (header.name.toLowerCase() == to_modify.header_name.toLowerCase()) 
-						{
-						if (config.debug_mode) log("Modify request header :  name= " + to_modify.header_name + ",old value=" + header.value +  ",new value=" + to_modify.header_value + " for url " + e.url);
-						header.value = to_modify.header_value;
-						}
-					}
-				}
-			else if (to_modify.action=="delete")
-				{
-				var index = -1;
-			
-				for (var i=0; i < e.requestHeaders.length; i++)
-					{
-				 	if (e.requestHeaders[i].name.toLowerCase() == to_modify.header_name.toLowerCase())  index=i;
-					}
-				if (index!=-1) 
-					{
-					e.requestHeaders.splice(index,1);	
-					if (config.debug_mode) log("Delete request header :  name=" + to_modify.header_name.toLowerCase() + " for url " + e.url);
-					}
-				}
-			}
-	}
+  for (let to_modify of config.headers) {
+    if ((to_modify.status==="on")&&(to_modify.apply_on==="req")) {
+      if (to_modify.action==="add"){
+        let new_header = {"name" :to_modify.header_name,"value":to_modify.header_value};
+        e.requestHeaders.push(new_header);
+	if (config.debug_mode) log("Add request header : name=" + to_modify.header_name + ",value=" + to_modify.header_value + " for url " + e.url);
+      }
+      else if (to_modify.action==="modify") {
+	for (let header of e.requestHeaders) {
+          if (header.name.toLowerCase() === to_modify.header_name.toLowerCase()) {
+            if (config.debug_mode) log("Modify request header :  name= " + to_modify.header_name + ",old value=" + header.value +  ",new value=" + to_modify.header_value + " for url " + e.url);
+            header.value = to_modify.header_value;
+          }
+        }
+      }
+      else if (to_modify.action==="delete") {
+        let index = -1;
+        for (let i=0; i < e.requestHeaders.length; i++) {
+          if (e.requestHeaders[i].name.toLowerCase() === to_modify.header_name.toLowerCase())  index=i;
+        }
+	if (index!==-1) {
+          e.requestHeaders.splice(index,1);
+          if (config.debug_mode) log("Delete request header :  name=" + to_modify.header_name.toLowerCase() + " for url " + e.url);
+        }
+      }
+    }
+  }
   if (config.debug_mode) log("End modify request headers for url " + e.url);
   return {requestHeaders: e.requestHeaders};
 }
@@ -137,47 +118,35 @@ function rewriteRequestHeader(e)
 * Rewrite the response header (add , modify or delete)
 *
 */
-function rewriteResponseHeader(e) 
-{
+function rewriteResponseHeader(e) {
   if (config.debug_mode) log("Start modify response headers for url " + e.url);
-  for (var to_modify of config.headers)
-	{
-		if ((to_modify.status=="on")&&(to_modify.apply_on=="res"))
-			{
-			if (to_modify.action=="add")  
-				{
-					var new_header = {"name" :to_modify.header_name,"value":to_modify.header_value};
-					e.responseHeaders.push(new_header);
-					if (config.debug_mode) log("Add response header : name=" + to_modify.header_name + ",value=" + to_modify.header_value + " for url " + e.url);
-				}
-			else if (to_modify.action=="modify")
-				{
-				for (var header of e.responseHeaders) 
-					{
-					if (header.name.toLowerCase() == to_modify.header_name.toLowerCase())
-						{
-						if (config.debug_mode) log("Modify response header :  name= " + to_modify.header_name + ",old value=" + header.value +  ",new value=" + to_modify.header_value  + " for url " + e.url);
-						header.value = to_modify.header_value;
-						}
-					}
-				}
-			else if (to_modify.action=="delete")
-				{
-				var index = -1;
-			
-				for (var i=0; i < e.responseHeaders.length; i++)
-					{
-				 	if (e.responseHeaders[i].name.toLowerCase() == to_modify.header_name.toLowerCase())  index=i;
-					}
-				if (index!=-1) 
-					{
-					e.responseHeaders.splice(index,1);
-					if (config.debug_mode) log("Delete response header :  name=" + to_modify.header_name.toLowerCase() + " for url " + e.url);					
-					}
-				}
-			}
-
+  for (let to_modify of config.headers) {
+    if ((to_modify.status==="on")&&(to_modify.apply_on==="res")) {
+      if (to_modify.action==="add") {
+        let new_header = {"name" :to_modify.header_name,"value":to_modify.header_value};
+	e.responseHeaders.push(new_header);
+	if (config.debug_mode) log("Add response header : name=" + to_modify.header_name + ",value=" + to_modify.header_value + " for url " + e.url);
+      }
+      else if (to_modify.action==="modify") {
+        for (let header of e.responseHeaders) {
+          if (header.name.toLowerCase() === to_modify.header_name.toLowerCase()) {
+            if (config.debug_mode) log("Modify response header :  name= " + to_modify.header_name + ",old value=" + header.value +  ",new value=" + to_modify.header_value  + " for url " + e.url);
+            header.value = to_modify.header_value;
+          }
+        }
+      }
+      else if (to_modify.action==="delete") {
+        let index = -1;
+        for (let i=0; i < e.responseHeaders.length; i++) {
+          if (e.responseHeaders[i].name.toLowerCase() === to_modify.header_name.toLowerCase())  index=i;
 	}
+        if (index!==-1) {
+          e.responseHeaders.splice(index,1);
+          if (config.debug_mode) log("Delete response header :  name=" + to_modify.header_name.toLowerCase() + " for url " + e.url);					
+        }
+      }
+    }
+  }
   if (config.debug_mode) log("End modify response headers for url " + e.url);
   return {responseHeaders: e.responseHeaders};
 }
@@ -190,68 +159,54 @@ function rewriteResponseHeader(e)
 * if message is off : stop the modify header
 *
 **/
-function notify(message) 
-	{
-	if (message=="reload") 
-		{
-		if (config.debug_mode) log("Reload configuration");
-		config=JSON.parse(localStorage.getItem("config"));
-		if (started=="on")
-			{		
-			removeListener();
-			addListener();
-			}
-		}
-
-	else if (message=="off")
-		{
-		removeListener();
-		browser.browserAction.setIcon({ path: "icons/modify-32.png"});
-		started="off";
-		if (config.debug_mode) log("Stop modifying headers");
-		}
-
-	else if (message=="on")
-		{
-		addListener();
-		browser.browserAction.setIcon({ path: "icons/modify-green-32.png"});
-		started="on";
-		if (config.debug_mode) log("Start modifying headers");
-		}
-  	}
+function notify(message) {
+  if (message==="reload") {
+    if (config.debug_mode) log("Reload configuration");
+    config=JSON.parse(localStorage.getItem("config"));
+    if (started==="on") {		
+      removeListener();
+      addListener();
+    }
+  }
+  else if (message==="off") {
+    removeListener();
+    browser.browserAction.setIcon({ path: "icons/modify-32.png"});
+    started="off";
+    if (config.debug_mode) log("Stop modifying headers");
+  }
+  else if (message==="on") {
+    addListener();
+    browser.browserAction.setIcon({ path: "icons/modify-green-32.png"});
+    started="on";
+    if (config.debug_mode) log("Start modifying headers");
+  }
+}
 
 /*
 * Add rewriteRequestHeader as a listener to onBeforeSendHeaders, only for the target pages.
 * Add rewriteResponseHeader as a listener to onHeadersReceived, only for the target pages.
 * Make it "blocking" so we can modify the headers.
 */
-function addListener()
-	{
-	var target = config.target_page;
-
-	if ((target=="*")||(target=="")||(target==" ")) target="<all_urls>";
-	
-	browser.webRequest.onBeforeSendHeaders.addListener(rewriteRequestHeader,
+function addListener() {
+  let target = config.target_page;
+  if ((target==="*")||(target==="")||(target===" ")) target="<all_urls>";
+  browser.webRequest.onBeforeSendHeaders.addListener(rewriteRequestHeader,
                                           {urls: target.split(";")},
                                           ["blocking", "requestHeaders"]);
 
-	browser.webRequest.onHeadersReceived.addListener(rewriteResponseHeader,
+  browser.webRequest.onHeadersReceived.addListener(rewriteResponseHeader,
                                           {urls: target.split(";")},
                                           ["blocking", "responseHeaders"]);
-
-
-	}
+}
 
 
 /*
 * Remove the two listener 
 *
 */
-function removeListener()
-	{
-	browser.webRequest.onBeforeSendHeaders.removeListener(rewriteRequestHeader);
-	browser.webRequest.onHeadersReceived.removeListener(rewriteResponseHeader);
-
-	}
+function removeListener() {
+  browser.webRequest.onBeforeSendHeaders.removeListener(rewriteRequestHeader);
+  browser.webRequest.onHeadersReceived.removeListener(rewriteResponseHeader);
+}
 
 
diff --git a/popup/config.js b/popup/config.js
index 7a595987a5289df10319884c0ebcb3ee92501892..c2f255adbfd4e54096ecd18ca1b72fa6cb7e35d6 100644
--- a/popup/config.js
+++ b/popup/config.js
@@ -9,64 +9,57 @@
  */
 
 
-var line_number = 1;
-var started = "off";
-var show_comments = true;
-var header_name_field_size= 20;
-var header_value_field_size= 28;
-var comments_field_size= 28;
+let line_number = 1;
+let started = "off";
+let show_comments = true;
+let header_name_field_size= 20;
+let header_value_field_size= 28;
+let comments_field_size= 28;
 
 window.onload = function() {
 	// load configuration from local storage
-	var config = JSON.parse(localStorage.getItem("config"));
-
-
+	let config = JSON.parse(localStorage.getItem("config"));
 	if (config.debug_mode) document.getElementById("debug_mode").checked = true;
 
-	if (typeof config.show_comments == 'undefined') document.getElementById("show_comments").checked = true;	
+	if (typeof config.show_comments === 'undefined') document.getElementById("show_comments").checked = true;	
 	else if (config.show_comments) document.getElementById("show_comments").checked = true;	
 	else show_comments=false;
 		
-	for (var to_add of config.headers) appendLine(to_add.action,to_add.header_name,to_add.header_value,to_add.comment,to_add.apply_on,to_add.status);
-	document.getElementById('save_button').addEventListener('click',function (e) {save_data();});
-	document.getElementById('export_button').addEventListener('click',function (e) {export_data();});
-	document.getElementById('import_button').addEventListener('click',function (e) {import_data(e);});
+	for (let to_add of config.headers) appendLine(to_add.action,to_add.header_name,to_add.header_value,to_add.comment,to_add.apply_on,to_add.status);
+	document.getElementById('save_button').addEventListener('click',function (e) {saveData();});
+	document.getElementById('export_button').addEventListener('click',function (e) {exportData();});
+	document.getElementById('import_button').addEventListener('click',function (e) {importData(e);});
 	document.getElementById('parameters_button').addEventListener('click',function (e) {showParametersScreen();});
 	document.getElementById('add_button').addEventListener('click',function (e) {appendLine("add","-","-","","req","on");});
-	document.getElementById('start_img').addEventListener('click',function (e) {start_modify();});
+	document.getElementById('start_img').addEventListener('click',function (e) {startModify();});
 	document.getElementById('targetPage').value=config.target_page;
 	document.getElementById('targetPage').addEventListener('keyup',function (e) {checkTargetPageField();});
 	document.getElementById('exit_parameters_screen_button').addEventListener('click',function (e) {hideParametersScreen();});
 	
 	started = localStorage.getItem("started");
-	if (started=="on") document.getElementById("start_img").src = "img/stop.png";	
+	if (started==="on") document.getElementById("start_img").src = "img/stop.png";	
 	
-
 	document.getElementById('show_comments').addEventListener('click',function (e) {showCommentsClick();});
 	reshapeTable();	
-} ;
+} 
 
 
 /** PARAMETERS SCREEN MANAGEMENT **/
 
-function showParametersScreen()
-{
-document.getElementById('main_screen').hidden=true;
-document.getElementById('parameters_screen').hidden=false;
+function showParametersScreen() {
+  document.getElementById('main_screen').hidden=true;
+  document.getElementById('parameters_screen').hidden=false;
 }
 
-
-function hideParametersScreen()
-{
-document.getElementById('main_screen').hidden=false;
-document.getElementById('parameters_screen').hidden=true;
+function hideParametersScreen() {
+  document.getElementById('main_screen').hidden=false;
+  document.getElementById('parameters_screen').hidden=true;
 }
 
-function showCommentsClick()
-{
-if (document.getElementById('show_comments').checked) show_comments = true;
-else show_comments = false;
-reshapeTable();
+function showCommentsClick() {
+  if (document.getElementById('show_comments').checked) show_comments = true;
+  else show_comments = false;
+  reshapeTable();
 }
 
 /** END PARAMETERS SCREEN MANAGEMENT **/
@@ -77,103 +70,87 @@ reshapeTable();
 * Add a new configuration line on the UI 
 **/
 function appendLine(action,header_name,header_value,comment,apply_on,status) {
-
-var html = "<td><select class=\"form_control select_field\" id=\"select_action" + line_number + "\" disable=false><option value=\"add\">Add</option><option value=\"modify\">Modify</option><option value=\"delete\">Delete</option></select></td>";
-html = html + "<td><input class=\"form_control input_field\"  size=\"" + header_name_field_size + "\" id=\"header_name"+ line_number + "\"></input></td>";
-html = html + "<td><input class=\"form_control input_field\"  size=\"" + header_value_field_size + "\" id=\"header_value"+ line_number + "\"></input></td>";
-html = html + "<td";
-if (!show_comments) html=html+" hidden";
-html = html + "><input class=\"form_control input_field\"  size=\""+ comments_field_size+ "\" id=\"comment"+ line_number + "\"></input></td>";
-html = html + "<td><select class=\"form_control select_field\" id=\"apply_on" + line_number + "\"><option value=\"req\"> Request </option><option value=\"res\">Response</option></select></td>";
-html = html +  "<td><a href=\"#\" title=\"Activate/Descativate rule\" id=\"activate_button" + line_number + "\" class=\"btn btn-primary btn-sm\">ON  <span class=\"glyphicon glyphicon-ok\"></span></a></td>";
-html = html +  "<td><a href=\"#\" title=\"Move line up\" id=\"up_button" + line_number + "\" class=\"btn btn-default btn-sm\"> <span class=\"glyphicon glyphicon-arrow-up\"></span></a></td>"; 
-html = html +  "<td><a href=\"#\" title=\"Move line down\" id=\"down_button" + line_number + "\" class=\"btn btn-default btn-sm\"> <span class=\"glyphicon glyphicon-arrow-down\"></span></a></td>"; 
-html = html +  "<td><a href=\"#\" title=\"Delete line\" id=\"delete_button" + line_number + "\" class=\"btn btn-primary btn-sm\"> <span class=\"glyphicon glyphicon-trash\"></span></a></td>"; 
-
-var newTR = document.createElement("tr");
-newTR.id="line" + line_number;
-newTR.innerHTML = html;
-document.getElementById("config_tab").appendChild(newTR);
-document.getElementById("select_action"+line_number).value = action;
-document.getElementById("apply_on"+line_number).value = apply_on;
-document.getElementById("header_name"+line_number).value = header_name;
-document.getElementById("header_value"+line_number).value = header_value;
-document.getElementById("comment"+line_number).value = comment;
-
-var line_number_to_modify = line_number;
-document.getElementById('activate_button'+line_number).addEventListener('click',function (e) {switchActivateButton(line_number_to_modify)});
-setButtonStatus(document.getElementById('activate_button'+line_number),status);
-document.getElementById('delete_button'+line_number).addEventListener('click',function (e) {delete_line(line_number_to_modify)});
-document.getElementById('up_button'+line_number).addEventListener('click',function (e) {invert_line(line_number_to_modify,line_number_to_modify-1)});
-document.getElementById('down_button'+line_number).addEventListener('click',function (e) {invert_line(line_number_to_modify,line_number_to_modify+1)});
-line_number++;
+  let html = "<td><select class=\"form_control select_field\" id=\"select_action" + line_number + "\" disable=false><option value=\"add\">Add</option><option value=\"modify\">Modify</option><option value=\"delete\">Delete</option></select></td>";
+  html = html + "<td><input class=\"form_control input_field\"  size=\"" + header_name_field_size + "\" id=\"header_name"+ line_number + "\"></input></td>";
+  html = html + "<td><input class=\"form_control input_field\"  size=\"" + header_value_field_size + "\" id=\"header_value"+ line_number + "\"></input></td>";
+  html = html + "<td";
+  if (!show_comments) html=html+" hidden";
+  html = html + "><input class=\"form_control input_field\"  size=\""+ comments_field_size+ "\" id=\"comment"+ line_number + "\"></input></td>";
+  html = html + "<td><select class=\"form_control select_field\" id=\"apply_on" + line_number + "\"><option value=\"req\"> Request </option><option value=\"res\">Response</option></select></td>";
+  html = html +  "<td><a href=\"#\" title=\"Activate/Descativate rule\" id=\"activate_button" + line_number + "\" class=\"btn btn-primary btn-sm\">ON  <span class=\"glyphicon glyphicon-ok\"></span></a></td>";
+  html = html +  "<td><a href=\"#\" title=\"Move line up\" id=\"up_button" + line_number + "\" class=\"btn btn-default btn-sm\"> <span class=\"glyphicon glyphicon-arrow-up\"></span></a></td>"; 
+  html = html +  "<td><a href=\"#\" title=\"Move line down\" id=\"down_button" + line_number + "\" class=\"btn btn-default btn-sm\"> <span class=\"glyphicon glyphicon-arrow-down\"></span></a></td>"; 
+  html = html +  "<td><a href=\"#\" title=\"Delete line\" id=\"delete_button" + line_number + "\" class=\"btn btn-primary btn-sm\"> <span class=\"glyphicon glyphicon-trash\"></span></a></td>"; 
+
+  let newTR = document.createElement("tr");
+  newTR.id="line" + line_number;
+  newTR.innerHTML = html;
+  document.getElementById("config_tab").appendChild(newTR);
+  document.getElementById("select_action"+line_number).value = action;
+  document.getElementById("apply_on"+line_number).value = apply_on;
+  document.getElementById("header_name"+line_number).value = header_name;
+  document.getElementById("header_value"+line_number).value = header_value;
+  document.getElementById("comment"+line_number).value = comment;
+
+  const line_number_to_modify = line_number;
+  document.getElementById('activate_button'+line_number).addEventListener('click',function (e) {switchActivateButton(line_number_to_modify)});
+  setButtonStatus(document.getElementById('activate_button'+line_number),status);
+  document.getElementById('delete_button'+line_number).addEventListener('click',function (e) {deleteLine(line_number_to_modify)});
+  document.getElementById('up_button'+line_number).addEventListener('click',function (e) {invertLine(line_number_to_modify,line_number_to_modify-1)});
+  document.getElementById('down_button'+line_number).addEventListener('click',function (e) {invertLine(line_number_to_modify,line_number_to_modify+1)});
+  line_number++;
 }
 
 
 /** ACTIVATE BUTTON MANAGEMENT **/ 
 
-function setButtonStatus(button,status)
-{
-if (status=="on")
-	{
-	button.className="btn btn-primary btn-sm";
-	button.innerHTML="ON  <span class=\"glyphicon glyphicon-ok\"></span>";
-	}
-else
-	{
-	button.className="btn btn-default btn-sm";
-	button.innerHTML="OFF <span class=\"glyphicon glyphicon-ban-circle\"></span>";
-	}
+function setButtonStatus(button,status) {
+  if (status==="on") {
+    button.className="btn btn-primary btn-sm";
+    button.innerHTML="ON  <span class=\"glyphicon glyphicon-ok\"></span>";
+  }
+  else {
+    button.className="btn btn-default btn-sm";
+    button.innerHTML="OFF <span class=\"glyphicon glyphicon-ban-circle\"></span>"; 
+  }
 }
 
-function getButtonStatus(button)
-{
-if (button.className=="btn btn-primary btn-sm") return "on";
-return "off";
+function getButtonStatus(button) {
+  if (button.className==="btn btn-primary btn-sm") return "on";
+  return "off";
 }
 
 
-function switchActivateButton(button_number)
-{
-var activate_button = document.getElementById("activate_button"+button_number);
-
-// Button is ON 
-if (getButtonStatus(activate_button)=="on") setButtonStatus(activate_button,"off");
-
-// Button is OFF
-else setButtonStatus(activate_button,"on");
-
+function switchActivateButton(button_number) {
+  const activate_button = document.getElementById("activate_button"+button_number);
+  // Button is ON 
+  if (getButtonStatus(activate_button)==="on") setButtonStatus(activate_button,"off");
+  // Button is OFF
+  else setButtonStatus(activate_button,"on");
 }
 
 /** END ACTIVATE BUTTON MANAGEMENT **/ 
 
 
-/** Resahpe the table  **/
-
-function reshapeTable()
-{
-var th_elements = document.querySelectorAll("#config_table_head th");
-var tr_elements = document.querySelectorAll("#config_tab tr");
-if (show_comments) 
-	{
-	header_name_field_size= 20;
-	header_value_field_size= 28;
-	}
-else 
-	{
-	header_name_field_size= 34;
-	header_value_field_size= 42;
-	}
-
-for (i=0;i<tr_elements.length;i++)
-	{
-	tr_elements[i].childNodes[3].hidden = (!show_comments);
-	tr_elements[i].childNodes[2].childNodes[0].size=header_value_field_size;
-	tr_elements[i].childNodes[1].childNodes[0].size=header_name_field_size;
-	}
-
-th_elements[3].hidden = (!show_comments);
-
+/** Reshape the table  **/
+
+function reshapeTable() {
+  let th_elements = document.querySelectorAll("#config_table_head th");
+  let tr_elements = document.querySelectorAll("#config_tab tr");
+  if (show_comments) {
+    header_name_field_size= 20;
+    header_value_field_size= 28;
+  }
+  else {
+    header_name_field_size= 34;
+    header_value_field_size= 42;
+  }
+  for (i=0;i<tr_elements.length;i++) {
+    tr_elements[i].childNodes[3].hidden = (!show_comments);
+    tr_elements[i].childNodes[2].childNodes[0].size=header_value_field_size;
+    tr_elements[i].childNodes[1].childNodes[0].size=header_name_field_size; 
+  }
+  th_elements[3].hidden = (!show_comments);
 }
 
 
@@ -182,117 +159,108 @@ th_elements[3].hidden = (!show_comments);
 * Create a JSON String representing the configuration data 
 *
 **/
-function create_configuration_data()
-{
-	var tr_elements = document.querySelectorAll("#config_tab tr");
-	var headers = [];
-	var debug_mode=false;
-	var show_comments=false;
-	for (i=0;i<tr_elements.length;i++)
-		{
-	
-		var action = tr_elements[i].childNodes[0].childNodes[0].value;
-		var header_name = tr_elements[i].childNodes[1].childNodes[0].value;
-		var header_value = tr_elements[i].childNodes[2].childNodes[0].value;
-		var comment = tr_elements[i].childNodes[3].childNodes[0].value;
-		var apply_on = tr_elements[i].childNodes[4].childNodes[0].value;
-		var status = getButtonStatus(tr_elements[i].childNodes[5].childNodes[0]);
-		headers.push({action:action,header_name:header_name,header_value:header_value,comment:comment,apply_on:apply_on,status:status});
-		}
-	if (document.getElementById("debug_mode").checked) debug_mode=true ;
-	if (document.getElementById("show_comments").checked) show_comments=true ;	
-	var to_export = {format_version:"1.1",target_page:document.getElementById('targetPage').value,headers:headers,debug_mode:debug_mode,show_comments:show_comments};
-	return JSON.stringify(to_export);
+function create_configuration_data() {
+  let tr_elements = document.querySelectorAll("#config_tab tr");
+  let headers = [];
+  let debug_mode=false;
+  let show_comments=false;
+  for (i=0;i<tr_elements.length;i++) {
+    const action = tr_elements[i].childNodes[0].childNodes[0].value;
+    const header_name = tr_elements[i].childNodes[1].childNodes[0].value;
+    const header_value = tr_elements[i].childNodes[2].childNodes[0].value;
+    const comment = tr_elements[i].childNodes[3].childNodes[0].value;
+    const apply_on = tr_elements[i].childNodes[4].childNodes[0].value;
+    const status = getButtonStatus(tr_elements[i].childNodes[5].childNodes[0]);
+    headers.push({action:action,header_name:header_name,header_value:header_value,comment:comment,apply_on:apply_on,status:status});
+  }
+  if (document.getElementById("debug_mode").checked) debug_mode=true ;
+  if (document.getElementById("show_comments").checked) show_comments=true ;	
+  let to_export = {format_version:"1.1",target_page:document.getElementById('targetPage').value,headers:headers,debug_mode:debug_mode,show_comments:show_comments};
+  return JSON.stringify(to_export);
 }
 
 /**
-*  check if url pattern is valid , if not ,  set the font color to red
+*  check if url pattern is valid , if not set the font color to red
 **/
-function checkTargetPageField()
-{
-if (isTargetValid(document.getElementById('targetPage').value)) document.getElementById('targetPage').style.color="black";
-else document.getElementById('targetPage').style.color="red";
+function checkTargetPageField() {
+  if (isTargetValid(document.getElementById('targetPage').value)) document.getElementById('targetPage').style.color="black";
+  else document.getElementById('targetPage').style.color="red";
 }
 
 /**
 * check if url patterns are valid
 **/
-function isTargetValid(target)
-	{
-		if (target=="") return true;
-		if (target==" ") return true;
-		if (target=="*") return true;
-		targets=target.split(";");
-		for (i in targets)
-			{
-				if (!targets[i].match("(http|https|[\*]):\/\/([\*][\.][^\*]*|[^\*]*|[\*])\/")) return false;
-			}
-		return true;
-	}
+function isTargetValid(target) {
+  if (target==="") return true;
+  if (target===" ") return true;
+  if (target==="*") return true;
+  targets=target.split(";");
+  for (i in targets) {
+    if (!targets[i].match("(http|https|[\*]):\/\/([\*][\.][^\*]*|[^\*]*|[\*])\/")) return false;
+  }
+  return true;
+}
+
 /**
 * If url patterns are valid save the data to the local storage and restart modify header
 **/
 
-function save_data() 
-	{
-	if (!isTargetValid(document.getElementById('targetPage').value))
-		{
-			alert("Can not save configuration: Url patterns are invalid");
-			return false;
-		}
-	localStorage.setItem("config",create_configuration_data());
-	browser.runtime.sendMessage("reload");
-	return true;
-	}
+function saveData() {
+  if (!isTargetValid(document.getElementById('targetPage').value)) {
+    alert("Can not save configuration: Url patterns are invalid");
+    return false;
+  }
+  localStorage.setItem("config",create_configuration_data()); 
+  browser.runtime.sendMessage("reload");
+  return true;
+}
+
 /**
 * If url pattern is valid save the data in a file 
 **/
 
-function export_data()
-	{
-	if (!isTargetValid(document.getElementById('targetPage').value))
-		{
-			alert("Can not export : Url pattern  is invalid");
-			return;
-		}
-	// Save in local storage
-	save_data();
-	// Create file data
-	var to_export= create_configuration_data();
-	
-	// Create file to save 
-	var a         = document.createElement('a');
-	a.href        = 'data:attachment/json,' +  encodeURIComponent(to_export);
-	a.target      = 'download';
-	a.download    = 'SimpleModifyHeader.conf';
+function exportData() {
+  if (!isTargetValid(document.getElementById('targetPage').value)) {
+    alert("Can not export : Url pattern  is invalid");
+    return;
+  }
+
+  // Save in local storage
+  saveData();
+
+  // Create file data
+  let to_export= create_configuration_data();
 	
-	// use iframe "download" to put the link (in order not to be redirect in the parent frame)
-	var myf = document.getElementById("download");
-	myf = myf.contentWindow.document || myf.contentDocument;
-	myf.body.appendChild(a);
-	a.click();
-	}
+  // Create file to save 
+  let a         = document.createElement('a');
+  a.href        = 'data:attachment/json,' +  encodeURIComponent(to_export);
+  a.target      = 'download';
+  a.download    = 'SimpleModifyHeader.conf';
+
+  // use iframe "download" to put the link (in order not to be redirect in the parent frame)
+  let myf = document.getElementById("download");
+  myf = myf.contentWindow.document || myf.contentDocument;
+  myf.body.appendChild(a);
+  a.click();
+}
 	
 
 /**
 * Choose a file and import data from the choosen file
 *
 **/
-function import_data(evt)
-	{
-	// create an input field in the iframe
-	if (window.confirm("This will erase your actual configuration, do you want to continue ?"))
-		{
-		var input = document.createElement("input");
-		input.type="file";
-		input.addEventListener('change', readSingleFile, false);
-		var myf = document.getElementById("download");
-		myf = myf.contentWindow.document || myf.contentDocument;
-		myf.body.appendChild(input);
-		input.click();
-		}
-
-	}
+function importData(evt) {
+  // create an input field in the iframe
+  if (window.confirm("This will erase your actual configuration, do you want to continue ?")) {
+    let input = document.createElement("input");
+    input.type="file";
+    input.addEventListener('change', readSingleFile, false);
+    let myf = document.getElementById("download");
+    myf = myf.contentWindow.document || myf.contentDocument;
+    myf.body.appendChild(input);
+    input.click();
+  }
+}
 
 /**
 * Import data from a file
@@ -301,100 +269,81 @@ function import_data(evt)
 *
 **/
 
-function readSingleFile(e) 
-	{
-	var file = e.target.files[0];
-	if (!file) {
-    		return;
-  		}
-  	var reader = new FileReader();
-  	reader.onload = function(e) 
-		{
-    		var contents = e.target.result;
-		var config="";	
-		try
-			{
-			config = JSON.parse(contents);
-			
-			// check file format
-			if (config.format_version)
-				{
-				// if url pattern invalid , set to "" 
-				if (!isTargetValid(config.target_page)) config.target_page=""; 
-
-				// if format file is 1.0 , need to add the apply_on value 
-				if (config.format_version=="1.0") 
-					{
-					config.format_version="1.1";
-					for (var line of config.headers) line.apply_on="req";
-					config.debug_mode=false;
-					}
-
-				// store the conf in the local storage 
-				localStorage.setItem("config",JSON.stringify(config));
-				// load the new conf 
-				browser.runtime.sendMessage("reload");
-				// reload the configuration page with the new conf
-				document.location.href="config.html";
-				}
-			else 
-				{
-				// try modify header add-on file format  : array of {action,name,value,comment,enabled}
-				if (config[0].action)
-					{
-					var headers = [];
-					for (var line_to_load of config)
-						{
-						var enabled = "off"; 
-						if (line_to_load.enabled) enabled = "on"
-						if (line_to_load.action=="Filter") line_to_load.action="delete";
-						headers.push({action:line_to_load.action.toLowerCase(),header_name:line_to_load.name,header_value:line_to_load.value,comment:line_to_load.comment,apply_on:"req",status:enabled});
-						}
-					var to_load = {format_version:"1.1",target_page:"",headers:headers,debug_mode:false};
-					
-					// store the conf in the local storage 
-					localStorage.setItem("config",JSON.stringify(to_load));
-					// load the new conf 
-					browser.runtime.sendMessage("reload");
-					// reload the configuration page with the new conf
-					document.location.href="config.html";	
-					}
-				else  alert("invalid file format");
-				}
-			}
-		catch(error) 
-			{
-  			console.log(error);
-			alert("Invalid file format");
-			}
-  		};
-  	reader.readAsText(file);
-	}
+function readSingleFile(e) {
+  let file = e.target.files[0];
+  if (!file) return;
+  let reader = new FileReader();
+  reader.onload = function(e) {
+    let contents = e.target.result;
+    let config="";	
+    try {
+      config = JSON.parse(contents);
+      // check file format
+      if (config.format_version) {
+        // if url pattern invalid , set to "" 
+        if (!isTargetValid(config.target_page)) config.target_page=""; 
+        // if format file is 1.0 , need to add the apply_on value 
+        if (config.format_version==="1.0") {
+          config.format_version="1.1";
+          for (let line of config.headers) line.apply_on="req";
+          config.debug_mode=false;
+        }
+        // store the conf in the local storage 
+        localStorage.setItem("config",JSON.stringify(config));
+        // load the new conf 
+        browser.runtime.sendMessage("reload");
+        // reload the configuration page with the new conf
+        document.location.href="config.html";
+      }
+      else {
+        // try modify header add-on file format  : array of {action,name,value,comment,enabled}
+        if (config[0].action) {
+	  let headers = [];
+	  for (let line_to_load of config) {
+            var enabled = "off"; 
+            if (line_to_load.enabled) enabled = "on";
+	    if (line_to_load.action==="Filter") line_to_load.action="delete";			   headers.push({action:line_to_load.action.toLowerCase(),header_name:line_to_load.name,header_value:line_to_load.value,comment:line_to_load.comment,apply_on:"req",status:enabled});
+	  }
+	  let to_load = {format_version:"1.1",target_page:"",headers:headers,debug_mode:false};
+          // store the conf in the local storage 
+          localStorage.setItem("config",JSON.stringify(to_load));
+          // load the new conf 
+	  browser.runtime.sendMessage("reload");
+          // reload the configuration page with the new conf
+	  document.location.href="config.html";	
+        }
+        else  alert("invalid file format");
+      }
+    }
+    catch(error) {
+      console.log(error);
+      alert("Invalid file format");
+    }
+  };
+  reader.readAsText(file);
+}
 
 
 /**
 * Delete a configuration line on the UI 
 **/
-function delete_line(line_number_to_delete)
-	{
-	if (line_number_to_delete != line_number) 
-			{
-			for (i=line_number_to_delete;i<line_number-1;i++)
-				{
-				var j = i+1;
-				document.getElementById("select_action"+i).value = document.getElementById("select_action"+j).value;
-				document.getElementById("header_name"+i).value = document.getElementById("header_name"+j).value;
-				document.getElementById("header_value"+i).value = document.getElementById("header_value"+j).value;
-				document.getElementById("comment"+i).value = document.getElementById("comment"+j).value;
-				setButtonStatus(document.getElementById("activate_button"+i),getButtonStatus(document.getElementById("activate_button"+j)));
-				document.getElementById("apply_on"+i).value = document.getElementById("apply_on"+j).value;
-						
-				}
-			}
-	var Node_to_delete = document.getElementById("line"+(line_number-1));
-    	Node_to_delete.parentNode.removeChild(Node_to_delete);
-	line_number--;
-	}
+function deleteLine(line_number_to_delete) {
+  if (line_number_to_delete !== line_number) {
+    for (i=line_number_to_delete;i<line_number-1;i++) {
+      const j = i+1;
+      document.getElementById("select_action"+i).value = document.getElementById("select_action"+j).value;
+      document.getElementById("header_name"+i).value = document.getElementById("header_name"+j).value;
+      document.getElementById("header_value"+i).value = document.getElementById("header_value"+j).value;
+      document.getElementById("comment"+i).value = document.getElementById("comment"+j).value;
+      setButtonStatus(document.getElementById("activate_button"+i),getButtonStatus(document.getElementById("activate_button"+j)));
+      document.getElementById("apply_on"+i).value = document.getElementById("apply_on"+j).value;
+    }
+  }
+
+  let Node_to_delete = document.getElementById("line"+(line_number-1));
+  Node_to_delete.parentNode.removeChild(Node_to_delete);
+  line_number--;
+}
 
 
 /**
@@ -402,58 +351,51 @@ function delete_line(line_number_to_delete)
 **/
 
 
-function invert_line(line1, line2)
-	{
-	// if a line does not exist , do nothing
-	if ((line1==0)||(line2==0)||(line1>=line_number)||(line2>=line_number)) return;
-
-	// Save data for line 1 
-	var select_action1= document.getElementById("select_action"+line1).value;
-	var header_name1 = document.getElementById("header_name"+line1).value;
-	var header_value1= document.getElementById("header_value"+line1).value;
-	var comment1 = document.getElementById("comment"+line1).value;
-	var select_status1 = getButtonStatus(document.getElementById("activate_button"+line1));
-	var apply_on1 = document.getElementById("apply_on"+line1).value;
-
-	// Copy line 2 to line 1
-	document.getElementById("select_action"+line1).value = document.getElementById("select_action"+line2).value;
-	document.getElementById("header_name"+line1).value = document.getElementById("header_name"+line2).value;
-	document.getElementById("header_value"+line1).value = document.getElementById("header_value"+line2).value;
-	document.getElementById("comment"+line1).value = document.getElementById("comment"+line2).value;
-	setButtonStatus(document.getElementById("activate_button"+line1),getButtonStatus(document.getElementById("activate_button"+line2)));
-	document.getElementById("apply_on"+line1).value = document.getElementById("apply_on"+line2).value;
-
-	// Copy line 1 to line 2 
-	document.getElementById("select_action"+line2).value = select_action1;
-	document.getElementById("header_name"+line2).value = header_name1;
-	document.getElementById("header_value"+line2).value = header_value1;
-	document.getElementById("comment"+line2).value = comment1;
-	setButtonStatus(document.getElementById("activate_button"+line2),select_status1);
-	document.getElementById("apply_on"+line2).value = apply_on1;
-
-	}
+function invertLine(line1, line2) {
+  // if a line does not exist , do nothing
+  if ((line1===0)||(line2===0)||(line1>=line_number)||(line2>=line_number)) return;
+
+  // Save data for line 1 
+  const select_action1= document.getElementById("select_action"+line1).value;
+  const header_name1 = document.getElementById("header_name"+line1).value;
+  const header_value1= document.getElementById("header_value"+line1).value;
+  const comment1 = document.getElementById("comment"+line1).value;
+  const select_status1 = getButtonStatus(document.getElementById("activate_button"+line1));
+  const apply_on1 = document.getElementById("apply_on"+line1).value;
+
+  // Copy line 2 to line 1
+  document.getElementById("select_action"+line1).value = document.getElementById("select_action"+line2).value;
+  document.getElementById("header_name"+line1).value = document.getElementById("header_name"+line2).value;
+  document.getElementById("header_value"+line1).value = document.getElementById("header_value"+line2).value;
+  document.getElementById("comment"+line1).value = document.getElementById("comment"+line2).value;
+  setButtonStatus(document.getElementById("activate_button"+line1),getButtonStatus(document.getElementById("activate_button"+line2)));
+  document.getElementById("apply_on"+line1).value = document.getElementById("apply_on"+line2).value;
+
+  // Copy line 1 to line 2 
+  document.getElementById("select_action"+line2).value = select_action1;
+  document.getElementById("header_name"+line2).value = header_name1;
+  document.getElementById("header_value"+line2).value = header_value1;
+  document.getElementById("comment"+line2).value = comment1;
+  setButtonStatus(document.getElementById("activate_button"+line2),select_status1);
+  document.getElementById("apply_on"+line2).value = apply_on1;
+}
 
 /**
 * Stop or Start modify header
 **/
-function start_modify()
-	{
-	if (started=="off") 
-		{
-		if (save_data())
-			{
-			localStorage.setItem("started","on");
-			browser.runtime.sendMessage("on");
-			started = "on";
-			document.getElementById("start_img").src = "img/stop.png";		
-			}
-		}
-	else 
-		{
-		localStorage.setItem("started","off");
-		browser.runtime.sendMessage("off");
-		started = "off";
-		document.getElementById("start_img").src = "img/start.png";
-		}
-
-	}
+function startModify() {
+  if (started==="off") {
+    if (saveData()) {
+      localStorage.setItem("started","on");
+      browser.runtime.sendMessage("on");
+      started = "on";
+      document.getElementById("start_img").src = "img/stop.png";		
+    }
+  }
+  else {
+    localStorage.setItem("started","off");
+    browser.runtime.sendMessage("off");
+    started = "off";
+    document.getElementById("start_img").src = "img/start.png";
+  }
+}