Consistent use of arrow functions in JS library code. NFC (#22807)

Author: sbc100

src/library.js

@@ -1561,7 +1561,7 @@ addToLibrary({
 
   emscripten_has_asyncify: () => {{{ ASYNCIFY }}},
 
-  emscripten_debugger: function() { debugger },
+  emscripten_debugger: () => { debugger },
 
   emscripten_print_double__deps: ['$stringToUTF8', '$lengthBytesUTF8'],
   emscripten_print_double: (x, to, max) => {

src/library_async.js

@@ -632,7 +632,7 @@ addToLibrary({
   emscripten_scan_registers: (func) => {
     throw 'Please compile your program with async support in order to use asynchronous operations like emscripten_scan_registers';
   },
-  emscripten_fiber_swap: function(oldFiber, newFiber) {
+  emscripten_fiber_swap: (oldFiber, newFiber) => {
     throw 'Please compile your program with async support in order to use asynchronous operations like emscripten_fiber_swap';
   },
 #endif // ASYNCIFY

src/library_bootstrap.js

@@ -15,11 +15,12 @@ assert(Object.keys(LibraryManager.library).length === 0);
 addToLibrary({
   $callRuntimeCallbacks: () => {},
 
-  $ExitStatus__docs: '/** @constructor */',
-  $ExitStatus: function(status) {
-    this.name = 'ExitStatus';
-    this.message = 'Program terminated with exit(' + status + ')';
-    this.status = status;
+  $ExitStatus: class {
+    name = 'ExitStatus';
+    constructor(status) {
+      this.message = `Program terminated with exit(${status})`;
+      this.status = status;
+    }
   },
 
   $exitJS__deps: ['$ExitStatus'],

src/library_fs.js

@@ -31,7 +31,7 @@ addToLibrary({
     '$strError', '$ERRNO_CODES',
 #endif
   ],
-  $FS__postset: function() {
+  $FS__postset: () => {
     // TODO: do we need noFSInit?
     addAtInit(`
 if (!Module['noFSInit'] && !FS.initialized)

src/library_legacy.js

@@ -122,7 +122,7 @@ legacyFuncs = {
 #endif
 
   $stackTrace__deps: ['$jsStackTrace'],
-  $stackTrace: function() {
+  $stackTrace: () => {
     var js = jsStackTrace();
     if (Module['extraStackTrace']) js += '\n' + Module['extraStackTrace']();
     return js;

src/library_stack_trace.js

@@ -5,13 +5,11 @@
  */
 
 var LibraryStackTrace = {
-  $jsStackTrace: function() {
-    return new Error().stack.toString();
-  },
+  $jsStackTrace: () => new Error().stack.toString(),
 
   $getCallstack__deps: ['$jsStackTrace', '$warnOnce'],
   $getCallstack__docs: '/** @param {number=} flags */',
-  $getCallstack: function(flags) {
+  $getCallstack: (flags) => {
     var callstack = jsStackTrace();
 
     // Find the symbols in the callstack that corresponds to the functions that
@@ -99,7 +97,7 @@ var LibraryStackTrace = {
   },
 
   emscripten_get_callstack__deps: ['$getCallstack', '$lengthBytesUTF8', '$stringToUTF8'],
-  emscripten_get_callstack: function(flags, str, maxbytes) {
+  emscripten_get_callstack: (flags, str, maxbytes) => {
     var callstack = getCallstack(flags);
     // User can query the required amount of bytes to hold the callstack.
     if (!str || maxbytes <= 0) {
@@ -205,7 +203,7 @@ var LibraryStackTrace = {
   // must be able to unwind from a PC value that may no longer be on the
   // execution stack, and so we are forced to cache the entire call stack.
   emscripten_stack_snapshot__deps: ['$convertFrameToPC', '$UNWIND_CACHE', '$saveInUnwindCache', '$jsStackTrace'],
-  emscripten_stack_snapshot: function() {
+  emscripten_stack_snapshot: () => {
     var callstack = jsStackTrace().split('\n');
     if (callstack[0] == 'Error') {
       callstack.shift();

src/library_syscall.js

@@ -97,7 +97,7 @@ var SyscallsLibrary = {
   },
 
   $syscallGetVarargI__internal: true,
-  $syscallGetVarargI: function() {
+  $syscallGetVarargI: () => {
 #if ASSERTIONS
     assert(SYSCALLS.varargs != undefined);
 #endif
@@ -112,7 +112,7 @@ var SyscallsLibrary = {
 
   $syscallGetVarargP__internal: true,
 #if MEMORY64
-  $syscallGetVarargP: function() {
+  $syscallGetVarargP: () => {
 #if ASSERTIONS
     assert(SYSCALLS.varargs != undefined);
 #endif
@@ -568,9 +568,7 @@ var SyscallsLibrary = {
                   (writefds ? {{{ makeGetValue('writefds', 4, 'i32') }}} : 0) |
                   (exceptfds ? {{{ makeGetValue('exceptfds', 4, 'i32') }}} : 0);
 
-    var check = function(fd, low, high, val) {
-      return (fd < 32 ? (low & val) : (high & val));
-    };
+    var check = (fd, low, high, val) => fd < 32 ? (low & val) : (high & val);
 
     for (var fd = 0; fd < nfds; fd++) {
       var mask = 1 << (fd % 32);

src/library_trace.js

@@ -210,7 +210,7 @@ var LibraryTracing = {
   },
 
   emscripten_trace_record_allocation: (address, size) => {
-    if (typeof Module['onMalloc'] == 'function') Module['onMalloc'](address, size);
+    Module['onMalloc']?.(address, size);
     if (EmscriptenTrace.postEnabled) {
       var now = EmscriptenTrace.now();
       EmscriptenTrace.post([EmscriptenTrace.EVENT_ALLOCATE,
@@ -219,7 +219,7 @@ var LibraryTracing = {
   },
 
   emscripten_trace_record_reallocation: (old_address, new_address, size) => {
-    if (typeof Module['onRealloc'] == 'function') Module['onRealloc'](old_address, new_address, size);
+    Module['onRealloc']?.(old_address, new_address, size);
     if (EmscriptenTrace.postEnabled) {
       var now = EmscriptenTrace.now();
       EmscriptenTrace.post([EmscriptenTrace.EVENT_REALLOCATE,
@@ -228,7 +228,7 @@ var LibraryTracing = {
   },
 
   emscripten_trace_record_free: (address) => {
-    if (typeof Module['onFree'] == 'function') Module['onFree'](address);
+    Module['onFree']?.(address);
     if (EmscriptenTrace.postEnabled) {
       var now = EmscriptenTrace.now();
       EmscriptenTrace.post([EmscriptenTrace.EVENT_FREE,
@@ -266,7 +266,7 @@ var LibraryTracing = {
     }
   },
 
-  emscripten_trace_report_off_heap_data: function () {
+  emscripten_trace_report_off_heap_data: () => {
     function openal_audiodata_size() {
       if (typeof AL == 'undefined' || !AL.currentContext) {
         return 0;