Consistent use of typeof operator in JS library code. NFC (emscripten-core#16261)

I noticed that in some places we were using equality checks (==/!=) and
in others we were using identity checks (===/!==).

In general identity checks are safer, but since typeof is known to
always returns a string and the RHS of these checks is also always a
string we can choose to always prefer `!=` and `==` over `!==` and `===`
for the sake of code size (sad but true, we care that much about each
  byte of output).

Perhaps a better solution would be to teach closure compiler how to
remove the extra `=` when its know that both sides of the operator are
the same type already.. but that would be a much larger change.

Author: sbc100

src/Fetch.js

@@ -71,7 +71,7 @@ var Fetch = {
 #endif // ~FETCH_SUPPORT_INDEXEDDB
 
 #if FETCH_SUPPORT_INDEXEDDB
-    if (typeof ENVIRONMENT_IS_FETCH_WORKER === 'undefined' || !ENVIRONMENT_IS_FETCH_WORKER) addRunDependency('library_fetch_init');
+    if (typeof ENVIRONMENT_IS_FETCH_WORKER == 'undefined' || !ENVIRONMENT_IS_FETCH_WORKER) addRunDependency('library_fetch_init');
 #endif
   }
 }

src/IDBStore.js

@@ -6,9 +6,9 @@
 
 {
   indexedDB: function() {
-    if (typeof indexedDB !== 'undefined') return indexedDB;
+    if (typeof indexedDB != 'undefined') return indexedDB;
     var ret = null;
-    if (typeof window === 'object') ret = window.indexedDB || window.mozIndexedDB || window.webkitIndexedDB || window.msIndexedDB;
+    if (typeof window == 'object') ret = window.indexedDB || window.mozIndexedDB || window.webkitIndexedDB || window.msIndexedDB;
     assert(ret, 'IDBStore used, but indexedDB not supported');
     return ret;
   },

src/base64Decode.js

@@ -37,7 +37,7 @@ base64ReverseLookup[47] = 63; // '/'
 /** @noinline */
 function base64Decode(b64) {
 #if ENVIRONMENT_MAY_BE_NODE
-  if (typeof ENVIRONMENT_IS_NODE !== 'undefined' && ENVIRONMENT_IS_NODE) {
+  if (typeof ENVIRONMENT_IS_NODE != 'undefined' && ENVIRONMENT_IS_NODE) {
     var buf = Buffer.from(b64, 'base64');
     return new Uint8Array(buf.buffer, buf.byteOffset, buf.byteLength);
   }

src/base64Utils.js

@@ -8,7 +8,7 @@
  * Decodes a base64 string.
  * @param {string} input The string to decode.
  */
-var decodeBase64 = typeof atob === 'function' ? atob : function (input) {
+var decodeBase64 = typeof atob == 'function' ? atob : function (input) {
   var keyStr = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';
 
   var output = '';
@@ -43,7 +43,7 @@ var decodeBase64 = typeof atob === 'function' ? atob : function (input) {
 // Throws error on invalid input.
 function intArrayFromBase64(s) {
 #if ENVIRONMENT_MAY_BE_NODE
-  if (typeof ENVIRONMENT_IS_NODE === 'boolean' && ENVIRONMENT_IS_NODE) {
+  if (typeof ENVIRONMENT_IS_NODE == 'boolean' && ENVIRONMENT_IS_NODE) {
     var buf = Buffer.from(s, 'base64');
     return new Uint8Array(buf['buffer'], buf['byteOffset'], buf['byteLength']);
   }

src/cpuprofiler.js

@@ -533,7 +533,7 @@ var emscriptenCpuProfiler = {
 
   detectWebGLContext: function() {
     if (Module['canvas'] && Module['canvas'].GLctxObject && Module['canvas'].GLctxObject.GLctx) return Module['canvas'].GLctxObject.GLctx;
-    else if (typeof GLctx !== 'undefined') return GLctx;
+    else if (typeof GLctx != 'undefined') return GLctx;
     else if (Module.ctx) return Module.ctx;
     return null;
   },
@@ -570,7 +570,7 @@ var emscriptenCpuProfiler = {
     document.getElementById("toggle_webgl_profile").style.background = '#E1E1E1';
 
     for (var f in glCtx) {
-      if (typeof glCtx[f] !== 'function' || f.startsWith('real_')) continue;
+      if (typeof glCtx[f] != 'function' || f.startsWith('real_')) continue;
       var realf = 'real_' + f;
       glCtx[f] = glCtx[realf];
       delete glCtx[realf];
@@ -603,8 +603,8 @@ var emscriptenCpuProfiler = {
   hookWebGL: function(glCtx) {
     if (!glCtx) glCtx = this.detectWebGLContext();
     if (!glCtx) return;
-    if (!((typeof WebGLRenderingContext !== 'undefined' && glCtx instanceof WebGLRenderingContext)
-     || (typeof WebGL2RenderingContext !== 'undefined' && glCtx instanceof WebGL2RenderingContext))) {
+    if (!((typeof WebGLRenderingContext != 'undefined' && glCtx instanceof WebGLRenderingContext)
+     || (typeof WebGL2RenderingContext != 'undefined' && glCtx instanceof WebGL2RenderingContext))) {
       document.getElementById("toggle_webgl_profile").disabled = true;
       return;
     }
@@ -619,7 +619,7 @@ var emscriptenCpuProfiler = {
     this.createSection(0, 'Hot GL', this.colorHotGLFunction, /*traceable=*/true);
     this.createSection(1, 'Cold GL', this.colorColdGLFunction, /*traceable=*/true);
     for (var f in glCtx) {
-      if (typeof glCtx[f] !== 'function' || f.startsWith('real_')) continue;
+      if (typeof glCtx[f] != 'function' || f.startsWith('real_')) continue;
       this.hookWebGLFunction(f, glCtx);
     }
     // The above injection won't work for texImage2D and texSubImage2D, which have multiple overloads.
@@ -671,4 +671,4 @@ setTimeout = (fn, delay) => {
 // Backwards compatibility with previously compiled code. Don't call this anymore!
 function cpuprofiler_add_hooks() { emscriptenCpuProfiler.initialize(); }
 
-if (typeof Module !== 'undefined' && typeof document !== 'undefined') emscriptenCpuProfiler.initialize();
+if (typeof Module != 'undefined' && typeof document != 'undefined') emscriptenCpuProfiler.initialize();

src/deterministic.js

@@ -11,7 +11,7 @@ Math.random = () => {
 };
 var TIME = 10000;
 Date.now = () => TIME++;
-if (typeof performance === 'object') performance.now = Date.now;
+if (typeof performance == 'object') performance.now = Date.now;
 if (ENVIRONMENT_IS_NODE) process['hrtime'] = Date.now;
 
 if (!Module) Module = {};

src/embind/embind.js

@@ -568,7 +568,7 @@ var LibraryEmbind = {
     var isUnsignedType = (name.includes('unsigned'));
     var checkAssertions = (value, toTypeName) => {
 #if ASSERTIONS
-        if (typeof value !== "number" && typeof value !== "boolean") {
+        if (typeof value != "number" && typeof value != "boolean") {
             throw new TypeError('Cannot convert "' + _embind_repr(value) + '" to ' + toTypeName);
         }
         if (value < minRange || value > maxRange) {
@@ -622,7 +622,7 @@ var LibraryEmbind = {
             return value;
         },
         'toWireType': function (destructors, value) {
-            if (typeof value !== "bigint") {
+            if (typeof value != "bigint") {
                 throw new TypeError('Cannot convert "' + _embind_repr(value) + '" to ' + this.name);
             }
             if (value < minRange || value > maxRange) {
@@ -653,7 +653,7 @@ var LibraryEmbind = {
         },
         'toWireType': function(destructors, value) {
 #if ASSERTIONS
-            if (typeof value !== "number" && typeof value !== "boolean") {
+            if (typeof value != "number" && typeof value != "boolean") {
                 throw new TypeError('Cannot convert "' + _embind_repr(value) + '" to ' + this.name);
             }
 #endif
@@ -726,7 +726,7 @@ var LibraryEmbind = {
             }
 
             var getLength;
-            var valueIsOfTypeString = (typeof value === 'string');
+            var valueIsOfTypeString = (typeof value == 'string');
 
             if (!(valueIsOfTypeString || value instanceof Uint8Array || value instanceof Uint8ClampedArray || value instanceof Int8Array)) {
                 throwBindingError('Cannot pass non-string to std::string');
@@ -827,7 +827,7 @@ var LibraryEmbind = {
             return str;
         },
         'toWireType': function(destructors, value) {
-            if (!(typeof value === 'string')) {
+            if (!(typeof value == 'string')) {
                 throwBindingError('Cannot pass non-string to C++ string type ' + name);
             }
 
@@ -1175,7 +1175,7 @@ var LibraryEmbind = {
     }
 
     var fp = makeDynCaller();
-    if (typeof fp !== "function") {
+    if (typeof fp != "function") {
         throwBindingError("unknown function pointer with signature " + signature + ": " + rawFunction);
     }
     return fp;

src/embind/emval.js

@@ -209,34 +209,34 @@ var LibraryEmVal = {
 
 #if DYNAMIC_EXECUTION == 0
   $emval_get_global: function() {
-    if (typeof globalThis === 'object') {
+    if (typeof globalThis == 'object') {
       return globalThis;
     }
     function testGlobal(obj) {
       obj['$$$embind_global$$$'] = obj;
-      var success = typeof $$$embind_global$$$ === 'object' && obj['$$$embind_global$$$'] === obj;
+      var success = typeof $$$embind_global$$$ == 'object' && obj['$$$embind_global$$$'] == obj;
       if (!success) {
         delete obj['$$$embind_global$$$'];
       }
       return success;
     }
-    if (typeof $$$embind_global$$$ === 'object') {
+    if (typeof $$$embind_global$$$ == 'object') {
       return $$$embind_global$$$;
     }
-    if (typeof global === 'object' && testGlobal(global)) {
+    if (typeof global == 'object' && testGlobal(global)) {
       $$$embind_global$$$ = global;
-    } else if (typeof self === 'object' && testGlobal(self)) {
+    } else if (typeof self == 'object' && testGlobal(self)) {
       $$$embind_global$$$ = self; // This works for both "window" and "self" (Web Workers) global objects
     }
-    if (typeof $$$embind_global$$$ === 'object') {
+    if (typeof $$$embind_global$$$ == 'object') {
       return $$$embind_global$$$;
     }
     throw Error('unable to get global object.');
   },
 #else
   // appease jshint (technically this code uses eval)
   $emval_get_global: function() {
-    if (typeof globalThis === 'object') {
+    if (typeof globalThis == 'object') {
       return globalThis;
     }
     return (function(){
@@ -491,13 +491,13 @@ var LibraryEmVal = {
   _emval_is_number__deps: ['$Emval'],
   _emval_is_number: function(handle) {
     handle = Emval.toValue(handle);
-    return typeof handle === 'number';
+    return typeof handle == 'number';
   },
 
   _emval_is_string__deps: ['$Emval'],
   _emval_is_string: function(handle) {
     handle = Emval.toValue(handle);
-    return typeof handle === 'string';
+    return typeof handle == 'string';
   },
 
   _emval_in__deps: ['$Emval'],

src/emrun_postjs.js

@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: MIT
  */
 
-if (typeof window === "object" && (typeof ENVIRONMENT_IS_PTHREAD === 'undefined' || !ENVIRONMENT_IS_PTHREAD)) {
+if (typeof window == "object" && (typeof ENVIRONMENT_IS_PTHREAD == 'undefined' || !ENVIRONMENT_IS_PTHREAD)) {
   var emrun_register_handlers = function() {
     // When C code exit()s, we may still have remaining stdout and stderr messages in flight. In that case, we can't close
     // the browser until all those XHRs have finished, so the following state variables track that all communication is done,
@@ -66,5 +66,5 @@ if (typeof window === "object" && (typeof ENVIRONMENT_IS_PTHREAD === 'undefined'
     http.send(data); // XXX  this does not work in workers, for some odd reason (issue #2681)
   };
 
-  if (typeof Module !== 'undefined' && typeof document !== 'undefined') emrun_register_handlers();
+  if (typeof Module != 'undefined' && typeof document != 'undefined') emrun_register_handlers();
 }

src/emrun_prejs.js

@@ -5,7 +5,7 @@
  */
 
 // Route URL GET parameters to argc+argv
-if (typeof window === 'object') {
+if (typeof window == 'object') {
   Module['arguments'] = window.location.search.substr(1).trim().split('&');
   // If no args were passed arguments = [''], in which case kill the single empty string.
   if (!Module['arguments'][0]) {