How can we delete array in javascript?

Posting Pro in Training

444 posts since Aug 2006

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wow i have created big javascript applications so far and yet i have never needed to delete something from memory. why do you need it?

serkan sendur

Postaholic

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2,062 posts since Jan 2008

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Hi everyone,

Lucky,
here's a simple demo, showing how you can removed items inside your array using the pop(index) method.

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
   "http://www.w3.org/TR/html4/loose.dtd">
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta http-equiv="Content-Script-Type" content="text/javascript">
<title>www.daniweb.com</title>
<script type="text/javascript">
<!--

window.onload = function() {
var bigArray = [];

   for ( var i = 0; i < 500; i++ ) { // creating 500 items into bigArray >>> 
      bigArray[ i ] = "Item" + i;
   } alert("bigArray has a total of " + ( bigArray.length ) + " items inside its collection");
   var aLen = ( bigArray.length - 1 ); 
   for ( var x = aLen; bigArray[ x ]; x-- ) { // Removing all 500 items from the bigArray.
      bigArray.pop( x ); 
   } alert( "\nAll items' from the ( bigArray ) has been removed.\nItem count: " + bigArray.length ); 
};
// --> 
</script>
</head>
<body>
<div></div>
</body>
</html>

essential

Posting Shark

974 posts since Aug 2008

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i dont think he is looking for such a processor consuming way of deleting the memory. i think delete keyword works better for his needs. or basically setting the array to null.

serkan sendur

Postaholic

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2,062 posts since Jan 2008

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Obtaining serkan's adviced of way of freeing the memory and minimized the above application:

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
   "http://www.w3.org/TR/html4/loose.dtd">
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta http-equiv="Content-Script-Type" content="text/javascript">
<title>www.daniweb.com</title>
<script type="text/javascript">
<!--

window.onload = function() {
   var bigArray = [];  
   bigArray2 = [];
   for ( var i = 0; i < 500; i++ ) { // creating 500 items into bigArray >>> 
      bigArray[ i ] = "Item" + i;
      bigArray2[ i ] = "Item" + i;
   } 
/*
  You can use the <strong>delete</strong> operator to delete variables declared implicitly but not those declared with the var statement. 

Output Sample: */

delete bigArray; // ignore's the delete process.

alert( bigArray.length ); // outputs the same length

// either one of the following statement will work, if you have defined it using the var statement.

bigArray = null; // or:

// bigArray = []; // reset's all items...

delete bigArray2; // this one works and delete's the bigArray2 variable.

};
// --> 
</script>
</head>
<body>
<div></div>
</body>
</html>

essential

Posting Shark

974 posts since Aug 2008

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0

Thanks for taking me into consideration :)

serkan sendur

Postaholic

Banned

2,062 posts since Jan 2008

Reputation Points: 854

Solved Threads: 127

-1

Thanks gentlemen,

So, using 'delete' OR '[]' will delete all the items (and memory) associated with the array.

Please confirm this.

Posting Pro in Training

444 posts since Aug 2006

Reputation Points: 83

Solved Threads: 61

-1

Hi lucky,

both ways will provide the same results, the only difference between the two procedure, is that when you use the delete operator, your variable will no longer be accessible within the function unless you redefined it.

Hope we've claimed your needs...

@serkan - welcome :), you had a better solution compared to my first post.

essential

Posting Shark

974 posts since Aug 2008

Reputation Points: 114

Solved Threads: 138

-1

wow i have created big javascript applications so far and yet i have never needed to delete something from memory. why do you need it?

We usually encounter this problem when working with embedded devices (settop boxes etc.) where there is very less memory. We need to free memory where ever its possible.

Posting Pro in Training

444 posts since Aug 2006

Reputation Points: 83

Solved Threads: 61

-1

Appreciated!
Thanks to all.