Backslash in regex strings in JavaScript

In strings with regexes, you need to escape (actually double) backslashes. Let's look at an example. Let's say we have the following string:

javascriptlet str = 'xyz';

Let's say we have the following code with regex:

javascriptlet reg = /\w+/;
let res = str.match(reg);

Let's convert the regular expression to a string. In this case, we have a problem with the backslash:

javascriptlet reg = new RegExp('\w+'); // doesn't work
let res = str.match(reg);

To solve the problem, double the backslash:

javascriptlet reg = new RegExp('\\w+'); // works
let res = str.match(reg);

Practical tasks

javascriptlet str = 'x1y x12y x123y';
let reg = /x\d+y/;
let res = str.replace(reg, '!');

javascriptlet str = 'x.y xay xby';
let reg = /x\.y/;
let res = str.replace(reg, '!');

javascriptlet str = 'x\\y';
let reg = /x\\y/;
let res = str.replace(reg, '!');