[jslib] Minor cleanups to JS library files. NFC (#27441)

Similar to #27425 but applied to the whole JS library

- Replace explicit zero checks (`=== 0`, `!== 0`) with implicit
truthy/falsy checks (`!x`, `x`).
- Replace `.length === 0` checks with `!arr.length`.
- Simplify null/undefined/zero check in `src/lib/libccall.js` to `if
(str)`.
- Use `for (var byte of data)` loop in `src/lib/libbrowser.js`.

Author: sbc100

src/lib/libasync.js

@@ -232,7 +232,7 @@ addToLibrary({
 #endif
       if (Asyncify.currData &&
           Asyncify.state === Asyncify.State.Unwinding &&
-          Asyncify.exportCallStack.length === 0) {
+          !Asyncify.exportCallStack.length) {
         // We just finished unwinding.
         // Be sure to set the state before calling any other functions to avoid
         // possible infinite recursion here (For example in debug pthread builds
@@ -548,7 +548,7 @@ addToLibrary({
 
       var entryPoint = {{{ makeGetValue('newFiber', C_STRUCTS.emscripten_fiber_s.entry, '*') }}};
 
-      if (entryPoint !== 0) {
+      if (entryPoint) {
 #if STACK_OVERFLOW_CHECK
         writeStackCookie();
 #endif

src/lib/libbootstrap.js

@@ -11,7 +11,7 @@
 assert(false, 'libbootstrap.js only designed for use with BOOTSTRAPPING_STRUCT_INFO')
 #endif
 
-assert(Object.keys(LibraryManager.library).length === 0);
+assert(!Object.keys(LibraryManager.library).length);
 addToLibrary({
   $callRuntimeCallbacks: () => {},
 

src/lib/libbrowser.js

@@ -107,8 +107,8 @@ var LibraryBrowser = {
               var ret = '';
               var leftchar = 0;
               var leftbits = 0;
-              for (var i = 0; i < data.length; i++) {
-                leftchar = (leftchar << 8) | data[i];
+              for (var byte of data) {
+                leftchar = (leftchar << 8) | byte;
                 leftbits += 8;
                 while (leftbits >= 6) {
                   var curr = (leftchar >> (leftbits-6)) & 0x3f;
@@ -601,7 +601,7 @@ var LibraryBrowser = {
     }
 #endif
 #if ASSERTIONS
-    assert(runDependencies === 0, 'async_load_script must be run when no other dependencies are active');
+    assert(!runDependencies, 'async_load_script must be run when no other dependencies are active');
 #endif
     {{{ runtimeKeepalivePush() }}}
 

src/lib/libccall.js

@@ -70,7 +70,7 @@ addToLibrary({
       for (var i = 0; i < args.length; i++) {
         var converter = toC[argTypes[i]];
         if (converter) {
-          if (stack === 0) stack = stackSave();
+          if (!stack) stack = stackSave();
           cArgs[i] = converter(args[i]);
         } else {
           cArgs[i] = args[i];
@@ -86,7 +86,7 @@ addToLibrary({
 #if ASYNCIFY == 1
       runtimeKeepalivePop();
 #endif
-      if (stack !== 0) stackRestore(stack);
+      if (stack) stackRestore(stack);
       return convertReturnValue(ret);
     }
 #if ASYNCIFY

src/lib/libcore.js

@@ -764,7 +764,10 @@ addToLibrary({
     var v4part = '';
     // check if the 10 high-order bytes are all zeros (first 5 words)
     for (i = 0; i < 5; i++) {
-      if (parts[i] !== 0) { hasipv4 = false; break; }
+      if (parts[i]) {
+        hasipv4 = false;
+        break;
+      }
     }
 
     if (hasipv4) {
@@ -777,7 +780,7 @@ addToLibrary({
         return str;
       }
       // IPv4-compatible IPv6 address if 16-bit value (bytes 11 and 12) == 0x0000 (6th word)
-      if (parts[5] === 0) {
+      if (!parts[5]) {
         str = '::';
         // special case IPv6 addresses
         if (v4part === '0.0.0.0') v4part = ''; // any/unspecified address
@@ -791,7 +794,7 @@ addToLibrary({
 
     // first run to find the longest contiguous zero words
     for (word = 0; word < 8; word++) {
-      if (parts[word] === 0) {
+      if (!parts[word]) {
         if (word - lastzero > 1) {
           len = 0;
         }
@@ -807,10 +810,10 @@ addToLibrary({
     for (word = 0; word < 8; word++) {
       if (longest > 1) {
         // compress contiguous zeros - to produce '::'
-        if (parts[word] === 0 && word >= zstart && word < (zstart + longest) ) {
+        if (!parts[word] && word >= zstart && word < (zstart + longest) ) {
           if (word === zstart) {
             str += ':';
-            if (zstart === 0) str += ':'; //leading zeros case
+            if (!zstart) str += ':'; //leading zeros case
           }
           continue;
         }
@@ -844,7 +847,7 @@ addToLibrary({
         var pathLen = salen - {{{ C_STRUCTS.sockaddr_un.sun_path }}};
         var path = '';
         if (pathLen > 0) {
-          if (HEAPU8[pathStart] === 0) {
+          if (!HEAPU8[pathStart]) {
             path = '\0' + UTF8ToString(pathStart + 1, pathLen - 1, /*ignoreNul=*/true);
           } else {
             // A pathname address is NUL-terminated; stop at the first NUL.
@@ -894,7 +897,7 @@ addToLibrary({
         // terminator), any other path is written NUL-terminated. An empty path
         // is the unnamed address (family only).
         addr ||= '';
-        var abstract = addr.charCodeAt(0) === 0;
+        var abstract = !addr.charCodeAt(0);
         // Pathname addresses include the trailing NUL in the reported length;
         // abstract addresses do not; an empty address is family-only (unnamed).
         var bytes = addr ? lengthBytesUTF8(addr) + (abstract ? 0 : 1) : 0;
@@ -1067,10 +1070,10 @@ addToLibrary({
 
     // If type or proto are set to zero in hints we should really be returning multiple addrinfo values, but for
     // now default to a TCP STREAM socket so we can at least return a sensible addrinfo given NULL hints.
-    if (proto === 0) {
+    if (!proto) {
       proto = {{{ cDefs.IPPROTO_TCP }}};
     }
-    if (type === 0) {
+    if (!type) {
       type = {{{ cDefs.SOCK_STREAM }}};
     }
 
@@ -1081,14 +1084,14 @@ addToLibrary({
         {{{ cDefs.AI_NUMERICSERV }}}|{{{ cDefs.AI_V4MAPPED }}}|{{{ cDefs.AI_ALL }}}|{{{ cDefs.AI_ADDRCONFIG }}})) {
       return {{{ cDefs.EAI_BADFLAGS }}};
     }
-    if (hint !== 0 && ({{{ makeGetValue('hint', C_STRUCTS.addrinfo.ai_flags, 'i32') }}} & {{{ cDefs.AI_CANONNAME }}}) && !node) {
+    if (hint && ({{{ makeGetValue('hint', C_STRUCTS.addrinfo.ai_flags, 'i32') }}} & {{{ cDefs.AI_CANONNAME }}}) && !node) {
       return {{{ cDefs.EAI_BADFLAGS }}};
     }
     if (flags & {{{ cDefs.AI_ADDRCONFIG }}}) {
       // TODO
       return {{{ cDefs.EAI_NONAME }}};
     }
-    if (type !== 0 && type !== {{{ cDefs.SOCK_STREAM }}} && type !== {{{ cDefs.SOCK_DGRAM }}}) {
+    if (type && type !== {{{ cDefs.SOCK_STREAM }}} && type !== {{{ cDefs.SOCK_DGRAM }}}) {
       return {{{ cDefs.EAI_SOCKTYPE }}};
     }
     if (family !== {{{ cDefs.AF_UNSPEC }}} && family !== {{{ cDefs.AF_INET }}} && family !== {{{ cDefs.AF_INET6 }}}) {
@@ -1113,7 +1116,7 @@ addToLibrary({
       if (family === {{{ cDefs.AF_UNSPEC }}}) {
         family = {{{ cDefs.AF_INET }}};
       }
-      if ((flags & {{{ cDefs.AI_PASSIVE }}}) === 0) {
+      if (!(flags & {{{ cDefs.AI_PASSIVE }}})) {
         if (family === {{{ cDefs.AF_INET }}}) {
           addr = _htonl({{{ cDefs.INADDR_LOOPBACK }}});
         } else {
@@ -1263,7 +1266,7 @@ addToLibrary({
     // to add extra entries from /etc/protocols if desired - though not sure if that'd actually be useful.
     var list = Protocols.list;
     var map  = Protocols.map;
-    if (list.length === 0) {
+    if (!list.length) {
         var entry = allocprotoent('tcp', 6, ['TCP']);
         list.push(entry);
         map['tcp'] = map['6'] = entry;
@@ -1739,7 +1742,7 @@ addToLibrary({
     var parts = trace.split('\n');
     for (var i = 0; i < parts.length; i++) {
       var ret = {{{ makeDynCall('iii', 'func') }}}(0, arg);
-      if (ret !== 0) return;
+      if (ret) return;
     }
   },
 
@@ -2364,7 +2367,7 @@ addToLibrary({
     assert(id, 'addRunDependency requires an ID')
     assert(!runDependencyTracking[id]);
     runDependencyTracking[id] = 1;
-    if (runDependencyWatcher === null && globalThis.setInterval) {
+    if (!runDependencyWatcher && globalThis.setInterval) {
       // Check for missing dependencies every few seconds
       runDependencyWatcher = setInterval(() => {
         if (ABORT) {

src/lib/libdylink.js

@@ -478,7 +478,7 @@ var LibraryDylink = {
 
     if (binary instanceof WebAssembly.Module) {
       var dylinkSection = WebAssembly.Module.customSections(binary, 'dylink.0');
-      failIf(dylinkSection.length === 0, 'need dylink section');
+      failIf(!dylinkSection.length, 'need dylink section');
       binary = new Uint8Array(dylinkSection[0]);
       end = binary.length
     } else {
@@ -490,7 +490,7 @@ var LibraryDylink = {
 #endif
       failIf(!magicNumberFound, 'need to see wasm magic number'); // \0asm
       // we should see the dylink custom section right after the magic number and wasm version
-      failIf(binary[8] !== 0, 'need the dylink section to be first')
+      failIf(binary[8], 'need the dylink section to be first')
       offset = 9;
       var section_size = getLEB(); // section size
       end = offset + section_size;

src/lib/libembind_gen.js

@@ -311,7 +311,7 @@ var LibraryEmbind = {
         out.push('  value: T;\n}\n');
       }
       out.push(`export type ${this.name} = `);
-      if (this.items.length === 0) {
+      if (!this.items.length) {
         out.push('never/* Empty Enumerator */');
       } else {
         const outItems = [];
@@ -715,7 +715,7 @@ var LibraryEmbind = {
                                             setter,
                                             setterContext) {
     fieldName = AsciiToString(fieldName);
-    const readonly = setter === 0;
+    const readonly = !setter;
     if (!(readonly || getterReturnType === setterArgumentType)) {
       throw new error('Mismatched getter and setter types are not supported.');
     }

src/lib/libembind_shared.js

@@ -195,7 +195,7 @@ var LibraryEmbindShared = {
 
   $getEnumValueType(rawValueType) {
     // This must match the values of enum_value_type in wire.h
-    return rawValueType === 0 ? 'object' : (rawValueType === 1 ? 'number' : 'string');
+    return !rawValueType ? 'object' : (rawValueType === 1 ? 'number' : 'string');
   },
 
   $getRequiredArgCount(argTypes) {

src/lib/libeventloop.js

@@ -290,7 +290,7 @@ LibraryJSEventLoop = {
     fakeRequestAnimationFrame(func) {
       // try to keep 60fps between calls to here
       var now = Date.now();
-      if (MainLoop.nextRAF === 0) {
+      if (!MainLoop.nextRAF) {
         MainLoop.nextRAF = now + 1000/60;
       } else {
         while (now + 2 >= MainLoop.nextRAF) { // fudge a little, to avoid timer jitter causing us to do lots of delay:0

src/lib/libexceptions.js

@@ -275,7 +275,7 @@ var LibraryExceptions = {
     // type of the thrown object. Find one which matches, and
     // return the type of the catch block which should be called.
     for (var caughtType of args) {
-      if (caughtType === 0 || caughtType === thrownType) {
+      if (!caughtType || caughtType === thrownType) {
         // Catch all clause matched or exactly the same type is caught
         break;
       }