在正则表达式替换字符串中转义$

Question

I want to turn the string dkfj-dkfj-sflj into dkfj-woop$dkfj-sflj .

Here's what I've tried:

var my_string = "dkfj-dkfj-sflj";
var regex = new RegExp("(\\w+)-(\\w+)-(\\w+)", "g");
console.log(my_string.replace(regex, "$1$woop[\$$2]$3");

And my result is: dkfj-woop$2-sflj . Because the "$" is in front of the "$2" capture group, it messes up that capture group.

Assuming I want the structure of my regex and capture group string to stay the same, what's the right way to escape that "$" so it works?

Answer 1

That isn't how you escape a $ for replace . Backslash escaping works at the parser level, functions like replace cannot give special meaning to new escape sequences like \\$ because they don't even see the \\$ . The string "\\$" is exactly equivalent to the string "$" , both produce the same string. If you wanted to pass a backslash and a dollar sign to a function, it's the backslash itself that requires escaping: "\\\\$" .

Regardless, replace expects you to escape a $ with $$ . You need "$1$woop[$$$2]$3" ; a $$ for the literal $ , and $2 for he capture group.

Read Specifying a string as a parameter in the replace docs.

Answer 2

Use $$ in the replacement part to print a literal $ symbol and you don't need to have a character class in the replacement part if your pattern was enclosed within forward slashes.

> var my_string = "dkfj-dkfj-sflj";
undefined
> my_string.replace(/(\w+)-\w+-(\w+)/, "$1-woop$$$1-$2")
'dkfj-woop$dkfj-sflj'