Nodejs Array Map map2(projection)

Here you can find the source of map2(projection)

Method Source Code

// https://egghead.io/lessons/javascript-the-array-map-method

const stocks= [//from   w w w . j  a  va2 s  . co  m
  {symbol: 'XFX', price: 240.22, volume: 23432},
  {symbol: 'TNZ', price: 332.19, volume: 234},
  {symbol: 'JXJ', price: 120.22, volume: 5323},
]

Array.prototype.map2= function(projection) {
  let results= []
  this.forEach(item => results.push(projection(item)))
  return results
}

const getStockSymbols= stocks => stocks.map2(stock => stock.symbol)

console.log('\nVIDEO 02')
console.log(JSON.stringify(getStockSymbols(stocks)))

Related

  1. map(projectionFunction)
    Array.prototype.map = function (projectionFunction) {
      var results = [];
      this.forEach(function (itemInArray) {
        results.push(projectionFunction(itemInArray));
      });
      return results;
    };
    
  2. map(projectionFunction)
    Array.prototype.map = function(projectionFunction) {
      var results = [];
      this.forEach(function(itemInArray) {
      });
      return results;
    };
    JSON.stringify(
      [1,2,3].map(function(x) {
        return x + 1;
    ...
    
  3. map(testFunction)
    Array.prototype.map = function(testFunction){
      var result = [];
      this.forEach(function(item){
        result.push(testFunction(item));
      })
      return result;
    
  4. map(transform)
    Array.prototype.map = function (transform) {
      let mappedArray = [];
      const len = this.length;
      for (let i = 0; i < len; i += 1) {
        mappedArray.push(transform(this[i], i, this));
      return mappedArray;
    };
    
  5. map(transformer)
    Array.prototype.map = function(transformer) {
      var result = []
      for ( var i = 0; i < this.length; i++) {
        result.push(transformer(this[i]));
      return result;
    
  6. mapByTwo(fun /*, thisp*/)
    Array.prototype.mapByTwo = function(fun ) {
      if (typeof fun != "function")
        throw new TypeError();
      var len = this.length >>> 0;
      var thisp = arguments[1];
      var k = 0;
      var A = new Array(Math.ceil(len/2));
      if (len/2 < A.length) {
        this.push(null);
    ...
    
  7. mapMe(func)
    Array.prototype.mapMe = function (func) {
      var arr = this, result = [];
      for (var i = 0; i < arr.length; i++) {
        result.push(func(arr[i]));
      return result;
    };
    
  8. mapValues(value)
    Array.prototype.mapValues = function(value) { 
        return this.map(function(e) { 
            return e[value] 
        })
    
  9. mapp(callback)
    Array.prototype.mapp = function(callback) {
      var newArray = [];
      for(var i = 0; i < this.length; i++){
        newArray.push(callback(this[i]));
      return newArray;
    var x = [1,2,3];
    x.mapp(function(ele) {
    ...