[Robustness] remove runtime dependency on all builtins except .apply

ljharb · ljharb · commit f743e61aa6bb · 2023-10-12T10:36:45.000-07:00
diff --git a/implementation.js b/implementation.js
@@ -3,23 +3,55 @@
 /* eslint no-invalid-this: 1 */
 
 var ERROR_MESSAGE = 'Function.prototype.bind called on incompatible ';
-var slice = Array.prototype.slice;
 var toStr = Object.prototype.toString;
+var max = Math.max;
 var funcType = '[object Function]';
 
+var concatty = function concatty(a, b) {
+    var arr = [];
+
+    for (var i = 0; i < a.length; i += 1) {
+        arr[i] = a[i];
+    }
+    for (var j = 0; j < b.length; j += 1) {
+        arr[j + a.length] = b[j];
+    }
+
+    return arr;
+};
+
+var slicy = function slicy(arrLike, offset) {
+    var arr = [];
+    for (var i = offset || 0, j = 0; i < arrLike.length; i += 1, j += 1) {
+        arr[j] = arrLike[i];
+    }
+    return arr;
+};
+
+var joiny = function (arr, joiner) {
+    var str = '';
+    for (var i = 0; i < arr.length; i += 1) {
+        str += arr[i];
+        if (i + 1 < arr.length) {
+            str += joiner;
+        }
+    }
+    return str;
+};
+
 module.exports = function bind(that) {
     var target = this;
-    if (typeof target !== 'function' || toStr.call(target) !== funcType) {
+    if (typeof target !== 'function' || toStr.apply(target) !== funcType) {
         throw new TypeError(ERROR_MESSAGE + target);
     }
-    var args = slice.call(arguments, 1);
+    var args = slicy(arguments, 1);
 
     var bound;
     var binder = function () {
         if (this instanceof bound) {
             var result = target.apply(
                 this,
-                args.concat(slice.call(arguments))
+                concatty(args, arguments)
             );
             if (Object(result) === result) {
                 return result;
@@ -28,18 +60,18 @@ module.exports = function bind(that) {
         }
         return target.apply(
             that,
-            args.concat(slice.call(arguments))
+            concatty(args, arguments)
         );
 
     };
 
-    var boundLength = Math.max(0, target.length - args.length);
+    var boundLength = max(0, target.length - args.length);
     var boundArgs = [];
     for (var i = 0; i < boundLength; i++) {
-        boundArgs.push('$' + i);
+        boundArgs[i] = '$' + i;
     }
 
-    bound = Function('binder', 'return function (' + boundArgs.join(',') + '){ return binder.apply(this,arguments); }')(binder);
+    bound = Function('binder', 'return function (' + joiny(boundArgs, ',') + '){ return binder.apply(this,arguments); }')(binder);
 
     if (target.prototype) {
         var Empty = function Empty() {};
