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JavaScript Arrays: Pushing, Popping and Shifting


This series of articles mainly concentrates on working with JavaScript arrays. This is the fourth article in the series and mainly concentrates on working with multiple arrays effectively. You can reuse these scripts to inject into server side controls easily (especially in .NET and Java).

Author Info:
By: Jagadish Chaterjee
Rating: 4 stars4 stars4 stars4 stars4 stars / 35
March 21, 2006
TABLE OF CONTENTS:
  1. · JavaScript Arrays: Pushing, Popping and Shifting
  2. · How to append an element to an array using JavaScript: discussion
  3. · How to pop (or delete at end) an element from an array using JavaScript
  4. · How to delete an element at the top from an array using JavaScript
  5. · How to add an element to the top of an array using JavaScript

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JavaScript Arrays: Pushing, Popping and Shifting - How to add an element to the top of an array using JavaScript
(Page 5 of 5 )

In this section I focus on “un-shifting” (also called “adding” at the beginning) an element to an array.

Now, let us try to develop a simple script (JavaScript) which adds (or un-shifts) a single element at the beginning of an array.  Have a look at the following code:

<html>
      <head>
            <meta  name=vs_targetSchema  content="http://schemas.microsoft.com/intellisense/ie5">
<script  id="clientEventHandlersJS"  language="javascript">
<!--
function Show()
{
      var myArray = new Array();
      myArray[0] = "Jag";
      myArray[1] = "Chat";
      myArray[2] = "Win";
      myArray[3] = "Dhan";
      document.write("Before un-shifting<br>-------------<br>");
      for (var i = 0; i < myArray.length; i++) 
      {
            document.write(myArray[i] + "<BR>");
      }
      myArray.unshift("aaa");
      document.write("<br>After un-shifting<br>-------------<br>");
      for (var i = 0; i < myArray.length; i++) 
      {
            document.write(myArray[i] + "<BR>");
      }
}

function Button1_onclick() {
      Show();
}
//-->
            </script>
      </head>
      <body>
      <form  id="form1">
                  <input  type="button"  value="Show"  id="Button1"  name="Button1"  onclick="return Button1_onclick()">
            </form>
      </body>
</html>

When the above code is executed, the following output is generated.

Before un-shifting
-------------
Jag
Chat
Win
Dhan

After un-shifting
-------------
aaa
Jag
Chat
Win
Dhan

The above code is very similar to the code available in the previous section with only the following change:

      myArray.unshift(“aaa”);

Earlier, in my first section, I used the “push” method.  When we apply “push” with a parameter, the parameter (or element) gets added to the array at the end (or gets appended).  The new method “unshift” is very similar to the method “push” except that it adds at the end.  Apart from this difference, the rest of the code is quite similar.

Summary

By now, I hope you are very clear about all the ways of working with arrays.  I used very simple examples, so that the clarity of the subject would be maintained with simplicity.  You can practice further by developing extended simple applications. 

You can have a few textboxes and lists on a web page and continuously add/delete/clear elements in an array dynamically with a few buttons, using all of the methods I described in this series.  I bet that it would really get you started with mastering arrays. 

Without mastering arrays in JavaScript, you would not be able to design and develop stunning web pages (unless you use design tools).  You can also develop several types of menus using JavaScript with the help of arrays, HTML and CSS together.  You can expect my articles on those subjects as well in the near future.

I shall start contributing again, on working with objects in JavaScript and finally implement arrays with objects (probably in a new series).  So, get back to this site frequently or sign up for a newsletter.

Any comments, suggestions, ideas, improvements, bugs, errors, feedback etc. are highly appreciated at jag_chat@yahoo.com.


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