What is the name and how to use this thing / \ in js?

Question

JavaScript

What is the name of this thing: /\
How does it work? After all, for example, in webpack.config.js, the following structure is written in the test field:
/\.js$/
or, for example, in search():

var str = "Mr. Blue has a blue house"
var n = str.search(/blue/i);

What is this thing anyway?

Answer 1

Regexp

Answer 2

To make the dot a symbol in the search string, the script looks for the string ".js" at the end of the text.