Placing variable in JavaScript regex

Question

I've got a regular expression like this one:

var reg = /http:\/\/s(\d+)\.de\.example\.com\/(.*?)\.php(.*)/i;

I want to have a variable, exactly this: ccode[i][2] in place of .de.

How do I do that? Thank for your help.

possible duplicate of How do you pass a variable to a Regular Expression JavaScript? — kamal pal
– kamal pal, Commented Jul 14, 2015 at 18:11

Wiktor Stribiżew · Accepted Answer · 2015-07-14 18:10:03Z

You need to use a RegExp constructor notation if you want to use variables in your regex pattern, and inside it, you need to double escape special regex metacharacters. I.e.

var reg = new RegExp("http://s(\\d+)\\." + ccode[i][2] + "\\.example\\.com/(.*?)\\.php(.*)", "i");

From MDN:

Use the constructor function when you know the regular expression pattern will be changing, or you don't know the pattern and are getting it from another source, such as user input.

Sample code:

var ccode = "de";
var reg = new RegExp("http://s(\\d+)\\." + ccode + "\\.example\\.com/(.*?)\\.php(.*)", "i");

alert(reg.test("http://s123.de.example.com/something.php?some=params"));

Keerthi · Accepted Answer · 2015-07-14 18:08:50Z

0

Try this

var reg = '/http:\/\/s(\d+)\\'+ccode[i][2]+'\.example\.com\/(.*?)\.php(.*)/i';

edited Jul 14, 2015 at 18:08

answered Jul 14, 2015 at 18:02

Keerthi

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1 Comment

Michał Gątkowski Over a year ago

I've tried it in console and.. Uncaught SyntaxError: Unexpected token ILLEGAL

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