JavaScript regex test if string contains specific word (with variable) [duplicate]

Question

I have a regex to check if a string contains a specific word. It works as expected:

/\bword\b/.test('a long text with the desired word amongst others'); // true
/\bamong\b/.test('a long text with the desired word amongst others'); // false

But i need the word which is about to be checked in a variable. Using new RegExp does not work properly, it always returns false:

var myString = 'a long text with the desired word amongst others';

var myWord = 'word';
new RegExp('\b' + myWord + '\b').test(myString); // false

myWord = "among";
new RegExp('\b' + myWord + '\b').test(myString); // false

What is wrong here?

user1106925 · Accepted Answer · 2012-04-10 18:02:47Z

33

var myWord = 'word';
new RegExp('\\b' + myWord + '\\b')

You need to double escape the \ when building a regex from a string.

This is because \ begins an escape sequence in a string literal, so it never makes it to the regex. By doing \\, you're including a literal '\' character in the string, which makes the regex /\bword\b/.

answered Apr 10, 2012 at 18:02

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user1106925

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3 Comments

Jonathan M Over a year ago

+1, see jsfiddle.net/TxQ7c/6

Alp Over a year ago

Figured it out at the same time you posted your answer. Thank you.

user1106925 Over a year ago

@Uri: Not sure what that has to do with this answer.

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