Nodejs Array Map map(projectionFunction)

Method Source Code

//http://reactivex.io/learnrx/
//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) {
      results.push(projectionFunction(itemInArray));
   });// w  w w.  ja  v  a  2s.c  o  m
   return results;
};

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

Related

1. map(mappingRelation)

   Array.prototype.map = function(mappingRelation){
     return this.reduce(function(accumulator, value){
       return accumulator.concat(mappingRelation(value));
     }, []);
   

2. map(projectionFunction)

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

3. map(projectionFunction)

   Array.prototype.map = function(projectionFunction) {
     var results = [];
     this.forEach(function(itemInArray) {
       results.push(itemInArray+1);
     });
     console.log(results);
     return results;
   };
   

4. map(projectionFunction)

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

5. map(projectionFunction)

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

6. map(projectionFunction)

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

7. 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);
   ...
   

8. map(projectionFunction)

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

9. map(projectionFunction)

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