[RESOLVED] Adding to array from for loop

**acbmse** · 05-30-2011 09:50 AM

Hi, When I try to write a value to the array, loop stops.

Code:

var colNums = new Array[5];

function multiplicationTable(){
	// Random Num Cols
	for (var i=0; i<5; i++){
		var randomColNum=Math.floor(Math.random()*100)+1;
		document.getElementById("col_"+i).innerHTML = randomColNum;	
		colNums[i]=randomColNum; //Trying to write value to array, stops loop
	}

Thanks for any help.

**vwphillips** · 05-30-2011 10:54 AM

Code:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">

<head>
  <title></title>
</head>

<body>
<script> vic=0; </script>
<form name=Show id=Show style="position:absolute;visibility:visible;top:700px;left:0px;" >
<input size=100 name=Show0 >
<input size=10 name=Show1 >
<input size=10 name=Show2 >
<input size=10 name=Show3 >
<input size=10 name=Show4 >
<input size=10 name=Show5 >
<input size=10 name=Show6 >
<input size=10 name=Show7 >
<input size=10 name=Show8 >
<input size=10 name=Show9 ><br>
<textarea name=TA rows=1 cols=100 ></textarea>
</form>
<script   type="text/javascript">
/*<![CDATA[*/
var colNums = [];

//function multiplicationTable(){
	// Random Num Cols
	for (var i=0; i<5; i++){
		var randomColNum=Math.floor(Math.random()*100)+1;
//		document.getElementById("col_"+i).innerHTML = randomColNum;
		colNums[i]=randomColNum; //Trying to write value to array, stops loop
	}
document.Show.Show0.value=colNums;
/*]]>*/
</script>
</body>

</html>

**acbmse** · 05-30-2011 11:07 AM

Changing:

Code:

var colNums = new Array[5];

To:

Code:

var colNums = new Array[5];

Did the trick.

Thank you.

**acbmse** · 05-30-2011 05:58 PM

I meant to var colNums = [5];
Can you tell me what I don't need 'new Array'?
Thank you.

**rnd me** · 05-31-2011 11:36 PM

Originally Posted by acbmse

I meant to var colNums = [5];
Can you tell me what I don't need 'new Array'?
Thank you.

colNums = [5] produces the following array: [5]...
you over-write the only element first thing in your loop, so you never noticed the 5. javascript expands arrays to their highest numbered index, so adding elements in a loop expands the array each cycle.

you really just need to say colNums= [];

**acbmse** · 06-01-2011 08:26 AM

Thanks so much. That makes sense.
I'm just starting to learn JavaScript and this is a big help.
Just one more question if you don't mind, why don't we use "new Array".

**acbmse** · 06-01-2011 09:56 AM

Sorry.
In my original code I used; var colNums = new Array[5];

When we change it to; var colNums = []; my script works.

So, I guess my question is, what is the difference in using 'new Array' in the var and not using it?

Hope this makes more sense

**rnd me** · 06-01-2011 02:28 PM

Originally Posted by acbmse

So, I guess my question is, what is the difference in using 'new Array' in the var and not using it?

(new Array) == ([])

just as

(new Object) == ({})

**acbmse** · 06-01-2011 02:45 PM

Thanks for your help

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