add apply

implementations/apply.js

@@ -0,0 +1,40 @@
+/*
+  The apply() method calls a function with a given this value, and arguments provided as an array (or an array-like object).
+
+
+  MDN Link: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/apply
+
+
+  Parameters
+
+  * otherThis
+    The value of this provided for the call to func. 
+  * arr
+    Optional. An array-like object, specifying the arguments with which func should be called, or null or undefined if no arguments should be provided to the function. 
+
+  Return value
+    The result of calling the function with the specified this value and arguments.
+*/
+
+Function.prototype.myApply = function (otherThis, arr) {
+  otherThis = otherThis || global;
+  var uniqueID = "00" + Math.random();
+  while (otherThis.hasOwnProperty(uniqueID)) {
+    uniqueID = "00" + Math.random();
+  }
+  otherThis[uniqueID] = this;
+
+  var args = [];
+  var result = null;
+  if (!arr) {
+    result = otherThis[uniqueID]();
+  } else {
+    for (let i = 1, len = arr.length; i < len; i++) {
+      args.push("arr[" + i + "]");
+    }
+    result = eval("otherThis[uniqueID](" + args + ")");
+  }
+
+  delete otherThis[uniqueID];
+  return result;
+};