Regex parenthesis Javascript

Question

Would someone please explain me why this returns false?

var regex = new RegExp('\([0-9]{3}\)[0-9]{3}-[0-9]{4}');
return regex.test('(555)555-5555');

Is there some other RegExp property that I have to insert?

Is it better not to use the string and does it have any difference using the string or the regex literal?

some · Accepted Answer · 2018-02-11T20:53:19.117

1

It returns false because you need to escape the backslash when you define it as a string, like this:

var rePhoneNumber = new RegExp('\\([0-9]{3}\\)[0-9]{3}-[0-9]{4}');

But, since it is javascript, you can make a literal definition:

var rePhoneNumber = /\([0-9]{3}\)[0-9]{3}-[0-9]{4}/;
return rePhoneNumber.test('(555)555-5555');

Now it return true, since you don't need to escape the backslash.

See a working snippet here:

var rePhoneNumber = /\([0-9]{3}\)[0-9]{3}-[0-9]{4}/;
console.log(rePhoneNumber.test('(555)555-5555'));

var rePhoneNumber2 = new RegExp('\\([0-9]{3}\\)[0-9]{3}-[0-9]{4}');
console.log(rePhoneNumber2.test('(555)555-5555'));

edited Feb 11 '18 at 20:53

answered Feb 11 '18 at 20:43

some

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how would I do that regex inside a string? Just for curiosity – Caio Gomes Feb 11 '18 at 20:49
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@Jan What the.... Oh. Why didn't I think of that? – some Feb 11 '18 at 20:49
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@some `Some` might have been in a hurry... – Jan Feb 11 '18 at 20:50
@CaioCésarSilvaGomes Added example of how to escape the string. – some Feb 11 '18 at 20:54

Regex parenthesis Javascript

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