Convert string into Regular Expression in Javascript [duplicate]

Question

From the backend of my application, I receive a regular expression which should be matched with a postal code in the frontend.

However, every time I convert to string into a regular expression using the RegExp class, I get another regular expression which doesn't match my postal code anymore.

This is the code I'm currently using (copy from my console):

var str = '/^[1-9][0-9]{3}\s?([a-zA-Z]{2})?$/',
exp = new RegExp(str);

// Returns null
'1055AA'.match(exp);

// The code below does work though...
// Returns: ["1055AA", "AA"]
'1055AA'.match(/^[1-9][0-9]{3}\s?([a-zA-Z]{2})?$/);

Can someone help me solve this problem? Thanks!

Escape the backslashes. '/^[1-9][0-9]{3}\\s?([a-zA-Z]{2})?$/' — Tushar
– Tushar, Commented Jan 10, 2016 at 12:17

Jongware · Accepted Answer · 2016-01-10 12:18:47Z

1

Your input string must not begin and end with the Regexp markers / - after all, it's a regular string, not a literal regexp. Also, since it's a regular string (and not (yet) a regexp), you need to double the backslashes as usual in a regular string.

answered Jan 10, 2016 at 12:18

Jongware

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2 Comments

T.J. Crowder Over a year ago

Good morning, Teej. Yeesh. Read right past 'em. If you think any of my now-deleted answer would be useful to add, feel free to grab it.

Vernon Over a year ago

Thanks! That helped a lot :)

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