Match dynamic string using regex

Question

I\'m trying to detect an occurrence of a string within string. But the code below always returns \"null\". Obviously something went wrong, but since I\'m a newbie, I can\'t

Answer 1

You're mixing up the two ways of creating regexes in JavaScript. If you use a regex literal, / is the regex delimiter, the g modifier immediately follows the closing delimiter, and \b is the escape sequence for a word boundary:

var regex = /width\b/g;

If you create it in the form of a string literal for the RegExp constructor, you leave off the regex delimiters, you pass modifiers in the form of a second string argument, and you have to double the backslashes in regex escape sequences:

var regex = new RegExp('width\\b', 'g');

The way you're doing it, the \b is being converted to a backspace character before it reaches the regex compiler; you have to escape the backslash to get it past JavaScript's string-literal escape-sequence processing. Or use a regex literal.