Error matching square bracket literal in string with JS regex

Question

I'm having an issue with matching a square bracket in a string with a regular expression in Javascript. I have tested the regex below, and it works for me:

"step_users[0][step][name]".match(/step_users\[\d*\]/)

This regex matches the substring "step_users[0]", but what I really need to match is the substring "step_users[0][step]". I tried modifying the regex as follows, but it fails for me.

/step_users\[\d*\]\[step\]/

In fact, if i even add on the second '[', it fails. So, this also fails:

"step_users[0][step][name]".match(/step_users\[\d*\]\[/)

Why would it match '[' for the first square bracket, but fail on the second?

Try give us a non-working jsFiddle.

gdoron
– gdoron

2012-03-20 07:47:46 +00:00
Commented Mar 20, 2012 at 7:47 — gdoron
– gdoron, Commented Mar 20, 2012 at 7:47

Zirak · Accepted Answer · 2012-03-20 07:48:55Z

2

You have a zero-width character in there!

"[0][".length === 5
"[0][".charCodeAt(3) === 8203

8203 is the word boundary character, a zero-width-space character. In fact, you have it between every pair of braces!

Remove it manually or dynamically as you fetch the data.

How I found it was simple. Your regex should have worked. So, I looked where it stopped working. An easy trick to find these zero-width spaces is to Shift-Arrow along the string.

Edit: A second after submitting, I thought of an easy way to remove it:

var destroyZWS = new RegExp(String.fromCharCode(8203), "g");
yourString.replace(destroyZWS, "");

This creates a regular expression, which globally searches for the specific ZWS character, and then replaces each occurrence with the empty string.

answered Mar 20, 2012 at 7:48

Zirak

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3 Comments

slave2zeros Over a year ago

Well...there we go then. Thanks. I suppose that's because I copied it out of the html name attribute output in my web inspector console.

Zirak Over a year ago

@slave2zeros Enjoy. I just edited in a simple way to remove that bugger.

slave2zeros Over a year ago

Well, normally they'll be coming from the name attribute of an HTML element, not copied from Safari's web inspector. It just happened to be a problem while testing in the console.

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