[thelist] Using for loops with a twist

Christian Heilmann codepo8 at gmail.com
Mon Apr 2 17:49:03 CDT 2007

<tip type="JavaScript for loops" author="Chris Heilmann">
In case you didn't know: The condition part of a JavaScript for loop
can be any condition, it does not need to compare the iterator. This
allows you for example to loop through an array without reading the

var arr = [1,2,0,4,5];
for(var i=0;arr[i];i++){

However, as 0 is falsy, you need to check properly:

var arr = [1,2,0,4,5];
for(var i=0;arr[i]!==undefined;i++){

More at http://www.wait-till-i.com/index.php?p=420

Chris Heilmann
Book: http://www.beginningjavascript.com
Blog: http://www.wait-till-i.com
Writing: http://icant.co.uk/

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