Nodejs Array Map map(projectionFunction)

Method Source Code

/*/*from  w  w  w. ja va2  s .c o  m*/
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));

   });

   return results;
};

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

Related

1. map(mapper)

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

2. map(mappingRelation)

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

3. map(projectionFunction)

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

7. map(projectionFunction)

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

8. 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);
   ...
   

9. map(projectionFunction)

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