How to use a variable value as a regex pattern

Question

I am desperate - I don't see what I'm doing wrong. I try to replace all occurrences of '8969' but I always get the original string (no matter whether tmp is a string or an int). Maybe it's already too late, maybe I'm blind, ...

var tmp = "8969";
alert("8969_8969".replace(/tmp/g, "99"));

Can someone help me out?

Why do you use such expression /tmp/g?

Lion
– Lion

2012-05-01 21:41:33 +00:00
Commented May 1, 2012 at 21:41 — Lion
– Lion, Commented May 1, 2012 at 21:41

Connell · Accepted Answer · 2012-05-01 21:40:42Z

8

The / characters are the container for a regular expression in this case. 'tmp' is therefore not used as a variable, but as a literal string.

var tmp = /8969/g;
alert("8969_8969".replace(tmp, "99"));

answered May 1, 2012 at 21:40

Connell♦

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Comments

gdoron · Accepted Answer · 2012-05-01 21:39:40Z

5

alert("8969_8969".replace(/8969/g, "99"));

or

var tmp = "8969"
alert("8969_8969".replace(new RegExp(tmp,"g"), "99"));

Live DEMO

answered May 1, 2012 at 21:39

gdoron

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1 Comment

user1000742 Over a year ago

I know this works, but I have the value in a variable ... Even if I write var tmp = 8969; it doesn't work ...

Gabe · Accepted Answer · 2012-05-01 21:41:15Z

3

Dynamic way of handling a regex:

var nRegExp = new RegExp("8969", 'g');
alert("8969_8969".replace(nRegExp, "99"));

answered May 1, 2012 at 21:41

Gabe

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Comments

gen_Eric · Accepted Answer · 2012-05-01 21:41:22Z

2

/tmp/g. This is a regex looking for the phrase "tmp". You need to use new RegExp to make a dynamic regex.

alert("8969_8969".replace(new RegExp(tmp,'g'), "99"));

answered May 1, 2012 at 21:41

gen_Eric

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Comments

FRD · Accepted Answer · 2013-06-08 20:09:34Z

-1

Javascript doesn't support that usage of tmp, it will try to use 'tmp' literally, as a regex pattern.

"8969_8969".replace(new RegExp(tmp,'g'), "99")

edited Jun 8, 2013 at 20:09

answered May 1, 2012 at 21:41

FRD

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