Issue 6745 - Prefer strict equality operator

lib/content/elemHideEmulation.js

Index: lib/content/elemHideEmulation.js
===================================================================
--- a/lib/content/elemHideEmulation.js
+++ b/lib/content/elemHideEmulation.js
@@ -22,33 +22,33 @@
 
 let MIN_INVOCATION_INTERVAL = 3000;
 const MAX_SYNCHRONOUS_PROCESSING_TIME = 50;
 const abpSelectorRegexp = /:-abp-([\w-]+)\(/i;
 
 function getCachedPropertyValue(object, name, defaultValueFunc = () => {})
 {
   let value = object[name];
-  if (typeof value == "undefined")
+  if (typeof value === "undefined")
     Object.defineProperty(object, name, {value: value = defaultValueFunc()});
   return value;
 }
 
 /** Return position of node from parent.
  * @param {Node} node the node to find the position of.
  * @return {number} One-based index like for :nth-child(), or 0 on error.
  */
 function positionInParent(node)
 {
   return indexOf(node.parentNode.children, node) + 1;
 }
 
 function makeSelector(node, selector = "")
 {
-  if (node == null)
+  if (!node)
     return null;
   if (!node.parentElement)
   {
     let newSelector = ":root";
     if (selector)
       newSelector += " > " + selector;
     return newSelector;
   }
@@ -67,34 +67,34 @@
 function parseSelectorContent(content, startIndex)
 {
   let parens = 1;
   let quote = null;
   let i = startIndex;
   for (; i < content.length; i++)
   {
     let c = content[i];
-    if (c == "\\")
+    if (c === "\\")
     {
       // Ignore escaped characters
       i++;
     }
     else if (quote)
     {
-      if (c == quote)
+      if (c === quote)
         quote = null;
     }
-    else if (c == "'" || c == '"')
+    else if (c === "'" || c === '"')
       quote = c;
-    else if (c == "(")
+    else if (c === "(")
       parens++;
-    else if (c == ")")
+    else if (c === ")")
     {
       parens--;
-      if (parens == 0)
+      if (parens === 0)
         break;
     }
   }
 
   if (parens > 0)
     return null;
   return {text: content.substring(startIndex, i), end: i};
 }
@@ -150,25 +150,25 @@
  * Query selector. If it is relative, will try :scope.
  * @param {Node} subtree the element to query selector
  * @param {string} selector the selector to query
  * @param {bool} [all=false] true to perform querySelectorAll()
  * @returns {?(Node|NodeList)} result of the query. null in case of error.
  */
 function scopedQuerySelector(subtree, selector, all)
 {
-  if (selector[0] == ">")
+  if (selector[0] === ">")
   {
     selector = ":scope" + selector;
     if (scopeSupported)
     {
       return all ? subtree.querySelectorAll(selector) :
         subtree.querySelector(selector);
     }
-    if (scopeSupported == null)
+    if (scopeSupported === null)
       return tryQuerySelector(subtree, selector, all);
     return null;
   }
   return all ? subtree.querySelectorAll(selector) :
     subtree.querySelector(selector);
 }
 
 function scopedQuerySelectorAll(subtree, selector)
@@ -350,18 +350,18 @@
       }
     }
   }
 };
 
 function PropsSelector(propertyExpression)
 {
   let regexpString;
-  if (propertyExpression.length >= 2 && propertyExpression[0] == "/" &&
-      propertyExpression[propertyExpression.length - 1] == "/")
+  if (propertyExpression.length >= 2 && propertyExpression[0] === "/" &&
+      propertyExpression[propertyExpression.length - 1] === "/")
   {
     regexpString = propertyExpression.slice(1, -1)
       .replace("\\7B ", "{").replace("\\7D ", "}");
   }
   else
     regexpString = filterToRegExp(propertyExpression);
 
   this._regexp = new RegExp(regexpString, "i");
@@ -377,17 +377,17 @@
         for (let subSelector of style.subSelectors)
         {
           if (subSelector.startsWith("*") &&
               !incompletePrefixRegexp.test(prefix))
           {
             subSelector = subSelector.substr(1);
           }
           let idx = subSelector.lastIndexOf("::");
-          if (idx != -1)
+          if (idx !== -1)
             subSelector = subSelector.substr(0, idx);
           yield prefix + subSelector;
         }
   },
 
   *getSelectors(prefix, subtree, styles)
   {
     for (let selector of this.findPropsSelectors(styles, prefix, this._regexp))
@@ -482,17 +482,17 @@
   let types = new Set();
 
   for (let mutation of mutations)
   {
     types.add(mutation.type);
 
     // There are only 3 types of mutations: "attributes", "characterData", and
     // "childList".
-    if (types.size == 3)
+    if (types.size === 3)
       break;
   }
 
   return types;
 }
 
 function filterPatterns(patterns, {stylesheets, mutations})
 {
@@ -527,33 +527,33 @@
   this.useInlineStyles = true;
 }
 
 ElemHideEmulation.prototype = {
   isSameOrigin(stylesheet)
   {
     try
     {
-      return new URL(stylesheet.href).origin == this.document.location.origin;
+      return new URL(stylesheet.href).origin === this.document.location.origin;
     }
     catch (e)
     {
       // Invalid URL, assume that it is first-party.
       return true;
     }
   },
 
   /** Parse the selector
    * @param {string} selector the selector to parse
    * @return {Array} selectors is an array of objects,
    * or null in case of errors.
    */
   parseSelector(selector)
   {
-    if (selector.length == 0)
+    if (selector.length === 0)
       return [];
 
     let match = abpSelectorRegexp.exec(selector);
     if (!match)
       return [new PlainSelector(selector)];
 
     let selectors = [];
     if (match.index > 0)
@@ -563,43 +563,43 @@
     let content = parseSelectorContent(selector, startIndex);
     if (!content)
     {
       console.error(new SyntaxError("Failed to parse Adblock Plus " +
                                     `selector ${selector} ` +
                                     "due to unmatched parentheses."));
       return null;
     }
-    if (match[1] == "properties")
+    if (match[1] === "properties")
       selectors.push(new PropsSelector(content.text));
-    else if (match[1] == "has")
+    else if (match[1] === "has")
     {
       let hasSelectors = this.parseSelector(content.text);
-      if (hasSelectors == null)
+      if (hasSelectors === null)
         return null;
       selectors.push(new HasSelector(hasSelectors));
     }
-    else if (match[1] == "contains")
+    else if (match[1] === "contains")
       selectors.push(new ContainsSelector(content.text));
     else
     {
       // this is an error, can't parse selector.
       console.error(new SyntaxError("Failed to parse Adblock Plus " +
                                     `selector ${selector}, invalid ` +
                                     `pseudo-class :-abp-${match[1]}().`));
       return null;
     }
 
     let suffix = this.parseSelector(selector.substr(content.end + 1));
-    if (suffix == null)
+    if (suffix === null)
       return null;
 
     selectors.push(...suffix);
 
-    if (selectors.length == 1 && selectors[0] instanceof ContainsSelector)
+    if (selectors.length === 1 && selectors[0] instanceof ContainsSelector)
     {
       console.error(new SyntaxError("Failed to parse Adblock Plus " +
                                     `selector ${selector}, can't ` +
                                     "have a lonely :-abp-contains()."));
       return null;
     }
     return selectors;
   },
@@ -666,17 +666,17 @@
         continue;
       }
 
       if (!rules)
         continue;
 
       for (let rule of rules)
       {
-        if (rule.type != rule.STYLE_RULE)
+        if (rule.type !== rule.STYLE_RULE)
           continue;
 
         cssStyles.push(stringifyStyle(rule));
       }
     }
 
     let pattern = null;
     let generator = null;
@@ -688,29 +688,29 @@
       if (!pattern)
       {
         if (!patterns.length)
         {
           if (selectors.length > 0)
             this.addSelectorsFunc(selectors, selectorFilters);
           if (elements.length > 0)
             this.hideElemsFunc(elements, elementFilters);
-          if (typeof done == "function")
+          if (typeof done === "function")
             done();
           return;
         }
 
         pattern = patterns.shift();
 
         generator = evaluate(pattern.selectors, 0, "",
                              this.document, cssStyles);
       }
       for (let selector of generator)
       {
-        if (selector != null)
+        if (selector !== null)
         {
           if (!this.useInlineStyles)
           {
             selectors.push(selector);
             selectorFilters.push(pattern.text);
           }
           else
           {
@@ -807,17 +807,17 @@
       {
         let params = Object.assign({}, this._scheduledProcessing);
         this._filteringInProgress = true;
         this._scheduledProcessing = null;
         this._addSelectors(params.stylesheets, params.mutations, completion);
       },
       MIN_INVOCATION_INTERVAL - (performance.now() - this._lastInvocation));
     }
-    else if (this.document.readyState == "loading")
+    else if (this.document.readyState === "loading")
     {
       this._scheduledProcessing = {stylesheets, mutations};
       let handler = () =>
       {
         this.document.removeEventListener("DOMContentLoaded", handler);
         let params = Object.assign({}, this._scheduledProcessing);
         this._filteringInProgress = true;
         this._scheduledProcessing = null;
@@ -845,17 +845,17 @@
   },
 
   apply(patterns)
   {
     this.patterns = [];
     for (let pattern of patterns)
     {
       let selectors = this.parseSelector(pattern.selector);
-      if (selectors != null && selectors.length > 0)
+      if (selectors !== null && selectors.length > 0)
         this.patterns.push(new Pattern(selectors, pattern.text));
     }
 
     if (this.patterns.length > 0)
     {
       this.queueFiltering();
       this.observer.observe(
         this.document,