JavaScript String replace - How do you use matched variables in the replacement string?

Question

How do you use the matched variables in the pattern in the replacement string?

var regexp = new RegExp('needle', 'ig');
str.replace(regexp, '<span class="marked">//1</span>')

Answer 1

try

var regexp = new RegExp(something, 'ig');
str.replace(regexp, '<span class="marked">$&</span>')

References:

• A table specifying the format of different tokens to be used into the replacement string

• An example on how to switch two words into a string

Answer 2

The correct way to use backreferences in JavaScript is via $1...$9.

To make your example work:

var regexp = new RegExp(something, 'ig');
var result = str.replace(regexp, '<span class="marked">$1</span>');

More information is available here: http://www.regular-expressions.info/javascript.html#replace