Nodejs Array Reduce reduce(testFunction,initialValue)

Method Source Code

Array.prototype.reduce = function(testFunction,initialValue){
   var accumulatedValue,counter;
   if(this.length == 0){
      return this;
   }else{/* w  w w  .  ja  v  a2 s.  c o m*/
      if(arguments.length == 1){
         counter = 1;
         accumulatedValue = this[0];
      }else if(arguments.length >= 2){
         counter = 0;
         accumulatedValue = initialValue;
      }else{
         throw 'Invalid arguments.'
      }

      while(counter < this.length){
         accumulatedValue = testFunction(accumulatedValue,this[counter]);
         console.log(accumulatedValue);
         counter++;
      }
      return [accumulatedValue];
   }

}


Array.prototype.map = function(testFunction){
   var result = [];
   this.forEach(function(item){
      result.push(testFunction(item));
   })
   return result;
}


(function(){
   var videos = [
      {
         "id": 65432445,
         "title": "The Chamber"
      },
      {
         "id": 675465,
         "title": "Fracture"
      },
      {
         "id": 70111470,
         "title": "Die Hard"
      },
      {
         "id": 654356453,
         "title": "Bad Boys"
      }
   ];

   return videos.
      reduce(function(acc,curr){
         var acc_copy = Object.create(acc);
         acc_copy[curr.id] = curr.title;
         return acc_copy;
      },{})
}());

Related

1. reduce(process, initial)

   Array.prototype.reduce = function(process, initial) {
     var value = initial;
     for (var i = 0; i < this.length; i++) {
       if( ( i === 0 ) && ( value === undefined || value === null ))
           value = this[0];
           continue;
       value = process( value, this[i] );
   ...
   

2. reduce(process, initial)

   Array.prototype.reduce = function(process, initial) {
     if (initial === undefined) {
       var slice = this.slice(1);
       initial = this[0];
     var array = slice || this;
     array.forEach(function(value) {
       initial = process(initial, value);
     });
   ...
   

3. reduce(reducingFunction, initialValue)

   Array.prototype.reduce = function(reducingFunction, initialValue) {
     var result = initialValue;
     this.forEach(function(x) {
       reducingFunction(result, x)
     });
     return result;
   

4. reduce(t, fn)

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

5. reduce(testFunction,initialValue)

   Array.prototype.reduce = function(testFunction,initialValue){
     var accumulatedValue,counter;
     if(this.length == 0){
       return this;
     }else{
       if(arguments.length == 1){
         counter = 1;
         accumulatedValue = this[0];
       }else if(arguments.length >= 2){
   ...
   

6. reduce(testFunction,initialValue)

   Array.prototype.reduce = function(testFunction,initialValue){
     var accumulatedValue,counter;
     if(this.length == 0){
       return this;
     }else{
       if(arguments.length == 1){
         counter = 1;
         accumulatedValue = this[0];
       }else if(arguments.length >= 2){
   ...
   

7. reduce.call(str, (trav, char)>

   'use strict';
   class PrefixTree {
       constructor() {
           this.root = {};
       insert(str) {
           Array.prototype.reduce.call(str, (trav, char) => {
               if (!trav[char]) {
                   trav[char] = {};
   ...
   

8. reduceRight(aggregate, initial)

   Array.prototype.reduceRight = function(aggregate, initial) {
     const len = this.length;
     let startIndex = len - 1;
     if(typeof initial === 'undefined') {
       initial = this[0];
       startIndex = len - 2;
     for(let i = startIndex; i >= 0; i -= 1) {
       initial = aggregate(initial, this[i], i, this);
   ...
   

9. reduceRight(fun /*, initial*/)

   Array.prototype.reduceRight = function(fun ) {
       var len = this.length >>> 0;
       if (typeof fun != "function") {
           throw new TypeError();
       if (len == 0 && arguments.length == 1) {
           throw new TypeError();
       var i = len - 1;
   ...