IE8’s Substr() Bug

I thought I would share this gotcha in the hope it saves the rest of the world some time. Here’s the deal……

In IE8 and below when using substr() to parse a string you cannot use -1 as the startIndex parameter: it will return NaN and error out. As an example, this will not work:-

var index = id.substr(-1, 1);

Instead you would need to do the following:-

var index = id.substr(id.length-1, 1);


Very small Yay!


1 comment so far

  1. Benito Aramando (@aramando) on

    Nice clean solution. Much more concise than Mozilla’s suggestion of overriding the substr function!

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