Nodejs Array Filter filter(predicateFunction)

Method Source Code

/*//from  w w  w .  ja va2  s . c  om
Exercise 7: Implement filter()

To make filtering easier, let's add a filter() function to the Array type. The
filter() function accepts a predicate. A predicate is a function that accepts
an item in the array, and returns a boolean indicating whether the item should
be retained in the new array.
*/

Array.prototype.filter = function(predicateFunction) {
   var results = [];
   this.forEach(function(itemInArray) {
     if (predicateFunction(itemInArray)) {
      results.push(itemInArray);
     }
   });

   return results;
};

// JSON.stringify([1,2,3].filter(function(x) { return x > 2})) === "[3]"

Related

1. filter(predicate)

   Array.prototype.filter = function(predicate) {
     var filtered_array = [];
     this.forEach(function (element, i) {
       if (predicate(element)) filtered_array.push(element);
     });
     return filtered_array;
   

2. filter(predicateFunction)

   Array.prototype.filter = function(predicateFunction) {
     var results = [];
     this.forEach(function(itemInArray) {
       if (predicateFunction(itemInArray)) {
       results.push(itemInArray);
     });
     return results;
   };
   ...
   

3. filter(predicateFunction)

   Array.prototype.filter = function(predicateFunction) {
     var results = [];
     this.forEach(function(itemInArray) {
       if(predicateFunction(itemInArray) == true)
         results.push(itemInArray);
     });
     return results;
   };
   

4. filter(predicateFunction)

   Array.prototype.filter = function(predicateFunction){
     var result = [];
     this.forEach(function(item){
       if(predicateFunction(item)) {
         result.push(item);
     })
     return result;
   Array.prototype.map = function(predicateFunction){
     var result = [];
     this.forEach(function(item){
       result.push(predicateFunction(item));
     })
     return result;
   var a = [1,2,3,4,5,6,7,8,9];
   a.map(function(x){
     return x*2;
   }).filter(function(x){
     if(x > 4) return true;
   })
   

5. filter(predicateFunction)

   var result = ['A','B','C','D','E','F'].filter(function(x) { 
     return x > 'C'
   });
   console.log(result);
   var outcome = JSON.stringify(result);
   console.log(outcome);
   var testOutCome = outcome === '["D","E","F"]';
   console.log(testOutCome);
   

6. filter(predicateFunction)

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

7. filter(predicateFunction)

   Array.prototype.filter = function(predicateFunction) {
     var results = [];
     this.forEach(function(itemInArray) {
       if (predicateFunction(itemInArray)) {
       results.push(itemInArray);
     });
     return results;
   };
   ...
   

8. filter(predicateFunction)

   Array.prototype.filter = function(predicateFunction) {
     var results = [];
     this.forEach(function(item) {
       if (predicateFunction(item)) {
         results.push(item);
     });
     return results;
   

9. filter(search, func)

   Array.prototype.filter = function(search, func) {
     var results = [];
     for(var i = 0; i < this.length; i++) {
       if(func(search, this[i]))
          results.push(this[i]);
     return results;