Javascript: Regex .test() for whitespace

Question

Strange regex result when looking for any white space characters

new RegExp('^[^\s]+$').test('aaa');
=> true

That's expected, but then...

new RegExp('^[^\s]+$').test('aaa  ');
=> true

How does that return true?

Answer 1

You need to escape \ in the string by \\. Otherwise, the generated regex would be /^[^s]+$/, which matches anything other than a string includes s.

new RegExp('^[^\\s]+$').test('aaa  ');

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Or you can use \S for matching anything other than whitespace.

new RegExp('^\\S+$').test('aaa  ');

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It would be better to use regex directly instead of parsing a regex string pattern.

/^[^\s]+$/.test('aaa  ');

// or

/^\S+$/.test('aaa  ');