Nodejs Array Map map(projectionFunction)

Method Source Code

// Exercise 4: Implement map()

// To make projections easier, let's add a map() function to the Array type. Map accepts the projection function to be applied to each item in the source array, and returns the projected array.

Array.prototype.map = function (projectionFunction) {
  var results = [];
  this.forEach(function (itemInArray) {

    // ------------ INSERT CODE HERE! ----------------------------
    // Apply the projectionFunction to each item in the array and add
    // each result to the results array.
    // Note: you can add items to an array with the push() method.
    results.push(projectionFunction(itemInArray));
    // ------------ INSERT CODE HERE! ----------------------------

  });//from  w w w.ja v a 2  s. c  o  m

  return results;
};

// JSON.stringify([1,2,3].map(function(x) { return x + 1; })) === '[2,3,4]'

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) {
       results.push(projectionFunction(itemInArray));
     });
     return results;
   };
   console.log(JSON.stringify([1,2,3].map(function(x) { return x + 1; }))) 
   

3. map(projectionFunction)

   Array.prototype.map = function(projectionFunction) {
     var results = [];
     this.forEach(function(itemInArray) {
       results.push(projectionFunction(itemInArray));
     });
     return results;
   };
   

4. map(projectionFunction)

   Array.prototype.map = function(projectionFunction) {
     var results = [];
     this.forEach(function(itemInArray) {
       results.push(projectionFunction(itemInArray));
     });
     return results;
   };
    var answer = JSON.stringify([1,2,3].map(function(x) { return x + 1; })) === '[2,3,4]';
    console.log(answer);
   ...
   

5. map(projectionFunction)

   Array.prototype.map = function(projectionFunction) {
     var results = [];
     this.forEach(itemInArray => results.push(projectionFunction(itemInArray)) );
     return results;
   };
   

6. 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;
   ...
   

7. map(testFunction)

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

8. 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;
   };
   

9. map(transformer)

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