Nodejs Array ForEach forEach(callback, thisArg)

Method Source Code

/**/*w  ww. j  a  v a 2 s .  co m*/
 * Array foreach()
 *
 * @Reference:
 * http://stackoverflow.com/questions/23614054/javascript-nuances-of-myarray-foreach-vs-for-loop
 * http://javascriptplayground.com/blog/2012/06/writing-javascript-polyfill/
 * http://www.2ality.com/2011/04/iterating-over-arrays-and-objects-in.html
 * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach
 *
 */

// Polyfill for forEach()
Array.prototype.forEach = function (callback, thisArg) {
  if (typeof callback !== 'function') {
    throw new TypeError(callback + ' is not a function.');
  }
  var len = this.length;  // Array length
  for (var i = 0; i < len; i++) {
    callback.call(thisArg, this[i], i, this);
  }
};

// Example of forEach()
function logArrayElements(currElement, currIndex, originalArray) {
  console.log('a[' + currIndex + '] = ' + currElement);
}

// Note there is no member at 2 so it isn't visited
[2, 5, , 9].forEach(logArrayElements);
// logs:
// a[0] = 2
// a[1] = 5
// a[3] = 9

Related

1. forEach(callback)

   Array.prototype.forEach = function(callback){
       let arr = this;
       for (var i = 0; i < arr.length; i++) {
           callback(arr[i], i, arr);
   

2. forEach(callback)

   Array.prototype.forEach = function(callback){
     var a = 0,
       len = this.length;
     while(a < len){
       callback(this[a], a++, this);
   };
   

3. forEach(callback)

   Array.prototype.forEach = Array.prototype.forEach || function (callback) {
       var self = this;
       for (var i = 0; i < self.length; i++) {
           var item = self[i];
           callback(item, i, self);
   

4. forEach(callback, context)

   Array.prototype.forEach = Array.prototype.forEach || function (callback, context) {
     context = context || window;
     var l = this.length;
     for (var i = 0; i < l; i++)
       callback.call(context, this[i], i, this);
   };
   

5. forEach(callback, context)

   Array.prototype.forEach = function (callback, context) {
       for (var index in this) {
           var item = this[index];
           if (!callback(index, item, context)) {
               break;
   };
   

6. forEach(cb)

   Array.prototype.forEach = function(cb){
     for(var k in this) cb(this[k]);
   };
   

7. forEach(cb)

   Array.prototype.forEach = function(cb) {
       for (var i = 0; i < this.length; i++) {
           cb(this[i]);
   };
   

8. forEach(cb)

   'use strict';
   Array.prototype.forEach = function(cb) {
     for(let i = 0 ; i < this.length ; i++) {
       cb(this[i]);
   };
   

9. forEach(fn)

   Array.prototype.forEach  = function(fn) {
     for (var i = 0; i < this.length; i++) fn(this[i]);