为什么String.raw可以处理双反斜杠，但不能正常转义？

Question

Matching double backslashes in a string requires two escape backslashes. But event that doesn't match in native JavaScript functions as can be seen below:

const str = 'sj\\sf\sd'

str.match(/\\\\/g);                  /*null*/
str.indexOf('\\\\');                 /*-1*/
str.replace(/\\\\/, '')              /*'sj\sfsd'*/   /*<--wrong characters replaced*/

Whereas String.raw works:

const str = String.raw`sj\\sf\sd`

str.match(/\\\\/g);                  /*['\\']*/
str.indexOf('\\\\');                 /*2*/
str.replace(String.raw`\\`, '')      /*'sjsf\sd'*/

Similar questions have been asked about this topic but none explain the reason behind this quirkiness:

• Replace double backslashes with a single backslash in javascript
• Javascript replacing double backslashed with single backslash

Answer 1

That's exactly what String.raw is for: it does not interpret escape sequences. A backslash has a special meaning in a string, so you need to double it to get one actual backslash. With String.raw , (most) special characters lose their special meaning, so two backslashes are actually two backslashes. It's used precisely when you need a string with many special characters and don't want to worry about escaping them correctly too much.