Question

How this is possible?

var re = /\w+/;

I have never seen something like this in any other language. Is this part of language sintax or something else? Leading ‘/’ is what I don’t understand, what exactly js does when it gets that with the “\w+/”?

Answer 1

It is a regular expression literal.

From the MDN docs

You construct a regular expression in one of two ways:

Using a regular expression literal, as follows:

var re = /ab+c/; 

Regular expression literals provide compilation of
the regular expression when the script is evaluated. When the regular
expression will remain constant, use this for better performance.

Calling the constructor function of the RegExp object, as follows: 1

var re = new RegExp("ab+c");

Using the constructor function provides runtime compilation of the regular expression. Use the constructor function when you know the regular expression pattern will be changing, or you don’t know the pattern and are getting it from another source, such as user input.