Javascript regex test from variable [duplicate]

Question

I have an problem with constructing regex from variable.

var a = '.playlist-item:nth-child(2n+1)';
var selector = /.playlist-item:nth-child\(2n\+1\)/g;
var s = '.playlist-item:nth-child\(2n\+1\)';

console.log(selector.test(a))//true

var reg = new RegExp(s,"g");
console.log(reg.test(a) )//false

Second is false because I have string quotes around it (I think), how do I construct regexp from string?

https://jsfiddle.net/eq3eu2e8/1/

You have to use double-\ in the regular expression string: '.playlist-item:nth-child\\(2n\\+1\\)' — Pointy
– Pointy, Commented Jul 17, 2016 at 14:09

Jacques Marais · Accepted Answer · 2016-07-17 14:18:06Z

3

For a string you have to use double backslashes if you want to include them in the string:

var a = '.playlist-item:nth-child(2n+1)';
var selector = /.playlist-item:nth-child\(2n\+1\)/g;
var s = '.playlist-item:nth-child\\(2n\\+1\\)';

console.log(selector.test(a)); //true

var reg = new RegExp(s,"g");
console.log(reg.test(a)); //false

answered Jul 17, 2016 at 14:18

Jacques Marais

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