Extending JavaScript Arrays

pradeep's Avatar author of Extending JavaScript Arrays
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This is an article on Extending JavaScript Arrays in JavaScript and AJAX.
All web developers require to implement some JavaScript in their web applications.
JavaScript arrays support a few in-built array manipulation methods like push,pop, but we might require more like unshift, shift, sort, shuffle, contains, clear and others.

In JavaScript array being an object, we can extend it.
Below you can find a few examples:

Implementing a simple bubble sort:

Code: javascript
Array.prototype.sort=function()
  {
      var tmp;
      for(var i=0;i<this.length;i++)
      {
          for(var j=0;j<this.length;j++)
          {
              if(this[i]<this[j])
              {
                  tmp = this[i];
                  this[i] = this[j];
                  this[j] = tmp;
              }
          }
      }
  };
Implementing ushift, which inserts an element into the beginning of the array.

Code: javascript
Array.prototype.unshift=function(item)
  {
      this[this.length] = null;/* create a new last element */
      for(var i=1;i<this.length;i++)
      {
          this[i] = this[i-1]; /* shift elements upwards */
      }
      this[0] = item;
  };
Implementing shift, which removes and returns the first element of an array.

Code: javascript
Array.prototype.shift=function()
  {
      for(var i=1;i<this.length;i++)
      {
          this[i-1] = this[i] /* shift element downwards */
      }
      this.length =  this.length-1;
  };
Implementing clear, which empties an array.

Code: javascript
Array.prototype.clear=function()
  {
      this.length = 0;
  };
Implementing contains, which checks where the specified elements exists in the array or not.

Code: javascript
Array.prototype.contains = function (element) 
  {
          for (var i = 0; i < this.length; i++) 
       {
              if (this[i] == element) 
          {
                      return true;
              }
          }
          return false;
  };
Continue to Extending JavaScript Arrays - Part 2
Newbie Member
6Apr2011,11:52   #2
krisper's Avatar
I know this is an old post, but since I found it anyone else might as well, so I'll just correct some of the mistakes I noticed.

Both the shift and unshift methods are flawed.
If we'd do the unshift method as shown here, we'd get the following:
say we want to add 1 to the array [2,3,4,5].
As the method suggests, we start with i=1 -> we copy number 2 from position 0 to 1;
next iteration i=2 -> there is number 2 on position 1 from last iteration, so we copy number 2 from position 1 to 2;
by now you already get the picture - in each iteration we copy the number 2 (or whatever you had on position 0 at the beginning) one position higher. After adding number 1 on the 0th position, we get the final array [1,2,2,2,2], which is now what we wanted.
here is a possible fix to that:

Array.prototype.unshift=function(item)
{
this[this.length] = null;/* create a new last element */
for(var i=this.length-1;i>0;i--)
{
this[i] = this[i-1]; /* shift elements upwards */
}
this[0] = item;
};

This will start coping items from the higher end and thus keeping the array and making room for the new first element.


As for the shift method - it doesn't return anything, although the description said it would return the first element of an array. Solution:

Array.prototype.shift=function()
{
var t = this[0];
for(var i=1;i<this.length;i++)
{
this[i-1] = this[i] /* shift element downwards */
}
this.length = this.length-1;
return t;
};

I anyone notices anything wrong with my fixes, go ahead and correct me - after all we're here to do thing the right way
Banned
7Nov2011,13:41   #3
mukeshsoftona's Avatar
Array of Integers



Code:
lass ArrayDemo {
     public static void main(String[] args) {
          int[] anArray;              // declares an array of integers

          anArray = new int[10];      // allocates memory for 10 integers
            
          anArray[0] = 100; // initialize first element
          anArray[1] = 200; // initialize second element
          anArray[2] = 300; // etc.
          anArray[3] = 400;
          anArray[4] = 500;
          anArray[5] = 600;
          anArray[6] = 700;
          anArray[7] = 800;
          anArray[8] = 900;
          anArray[9] = 1000;

          System.out.println("Element at index 0: " + anArray[0]);
          System.out.println("Element at index 1: " + anArray[1]);
          System.out.println("Element at index 2: " + anArray[2]);
          System.out.println("Element at index 3: " + anArray[3]);
          System.out.println("Element at index 4: " + anArray[4]);
          System.out.println("Element at index 5: " + anArray[5]);
          System.out.println("Element at index 6: " + anArray[6]);
          System.out.println("Element at index 7: " + anArray[7]);
          System.out.println("Element at index 8: " + anArray[8]);
          System.out.println("Element at index 9: " + anArray[9]);
     }
}
The output from this program is:

Element at index 0: 100
Element at index 1: 200
Element at index 2: 300
Element at index 3: 400
Element at index 4: 500
Element at index 5: 600
Element at index 6: 700
Element at index 7: 800
Element at index 8: 900
Element at index 9: 1000
Last edited by shabbir; 7Nov2011 at 14:36.. Reason: Code blocks
Newbie Member
7Nov2011,17:50   #4
krisper's Avatar
@mukeshsoftona How exactly is your post related to the previous messages?
Go4Expert Founder
7Nov2011,19:35   #5
shabbir's Avatar
Quote:
Originally Posted by krisper View Post
@mukeshsoftona How exactly is your post related to the previous messages?
Infraction given.