Nodejs Array Map map(callback)

Method Source Code

Array.prototype.map = function (callback) {
    var obj = this;
    var value, mapped_value;
    var A = new Array(obj.length);

    for (var i = 0; i < obj.length; i++) {
        value = obj[i];//from  w ww  .jav a  2s.co m
        mapped_value = callback.call(null, value);
        A[i] = mapped_value;
    }
    return A;
};

var arr = [1, 2, 3];
var new_arr = arr.map(function (value) {
    return value * value;
});

console.log(new_arr);

Related

1. map( func /*, obj */)

   Array.prototype.map = function(  func ) {
     var len = this.length;
     if (typeof func != 'function') {
       throw new Error("argument must be function");
     };
     var res = [];
     var obj = arguments[1];
     console.log("obj" + obj)
     for (var i = 0; i < len; i++) {
   ...
   

2. map( fn )

   Array.prototype.map = function( fn )
       var a = [];
       for( var i = 0; i < this.length; i++ ) {
           if( i in this ) a.push( fn( this[ i ] ) );
       return a;
   };
   

3. map(a)

   Array.prototype.map = function(a) {
     const array = new Array(this.length)
     for (let i = 0; i < this.length; i++) array[i] = a(this[i], i, this)
     return array
   

4. map(callback)

   Array.prototype.map = function(callback) {
     var result = [];
     for(var i = 0; i < this.length; i += 1) {
       result.push(callback.call(this[i]));
     return result;
   };
   

5. map(callback)

   Array.prototype.map = function(callback) {
     let res = [];
     this.forEach(el => res.push(callback(el)));
     return res;
   };
   let a = [1,2,3];
   let b = a.map(el => el * el);
   console.log(a);
   console.log(b);
   ...
   

6. map(callback)

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

7. map(callback)

   Array.prototype.map = function(callback){
       const newArr = []
       for(let i = 0; i < this.length; i += 1){
           let newValue = callback(this[i])
           newArr.push(newValue)
       return newArr
   var someArray = [1,2,3,4]
   ...
   

8. map(callback)

   Array.prototype.map = function(callback) {
     for(var i = 0, l = this.length; i < l; i++) {
       this[i] = callback(i, this[i]);
     return this;