How to concat a regex expression with a string variable?

Question

I have a regular expression as below:

var myVar = "some text";

var decimal = /^\s*(\+|-)?((\d+(\,\d+)?)|(\,\d+))\s*$/;

How to concat it with the myVar variable which is a string?

I tried the below but didn't work:

var decimal = new RegExp("/^\s*(\+|-)?((\d+(\" + myVar + "\d+)?)|(\" + myVar + "\d+))\s*$/");

Apologies, I updated what is required exactly. Basically the "," should be replaced with the myVar. — The Light
– The Light, Commented May 12, 2014 at 15:28
Are you basically trying to make a pattern that will match 1,23 in one locale and 1.23 in another? I'd suggest using some i18n library like this or this. — p.s.w.g
– p.s.w.g, Commented May 12, 2014 at 15:35

Samuel Caillerie · Accepted Answer · 2014-05-12 15:31:49Z

3

You don't need to add / at the beginning and the end of new RegExp(...) and \ should be escaped as mentioned by anubhava :

var decimal = new RegExp("^\\s*(\\+|-)?((\\d+(" + myVar + "\\d+)?)|(" + myVar + "\\d+))\\s*$");

answered May 12, 2014 at 15:25

Samuel Caillerie

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Comments

anubhava · Accepted Answer · 2014-05-12 15:27:23Z

2

Just from concatenation exercise you can do this:

var decimal = new RegExp("^(\\s*(\\+|-)?((\\d+(,\\d+)?)|(,\\d+))\\s*)" + myVar + "$");

Though keep in mind that myVar can contain special regex meta characters as well that need to be escaped.

answered May 12, 2014 at 15:27

anubhava

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Uri Agassi · Accepted Answer · 2014-05-12 15:34:41Z

0

You will need to escape the backslashes inside the string.

var decimal = new RegExp("/^\\s*(\\+|-)?((\\d+(\\,\\d+)?)|(\\,\\d+))\\s*$/" + myVar);

Uri Agassi

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answered May 12, 2014 at 15:30

nythgar

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