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?

Answer 1

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

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

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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/.