Remove comments from string with JavaScript using JavaScript

Question

There is some string (for example, 's'):

import 'lodash';
// TODO import jquery
//import 'jquery';

/*
Some very important comment
*/

How can I remove all comments from 's' string? Should I use some Regexp for it? I don't know.

Answer 1

The one from @MarcoS won't work in several cases...

Below is my solution:

str.replace(/\/\*[\s\S]*?\*\/|\/\/.*/g,'');

Removing comments from a string:

function removeComments(string){
    //Takes a string of code, not an actual function.
    return string.replace(/\/\*[\s\S]*?\*\/|\/\/.*/g,'').trim();//Strip comments
}
const commentedcode = `
alert('hello, this code has comments!')//An alert
/* A block comment here */
// A single line comment on a newline
`;
console.log(removeComments(commentedcode));

Using RegExr.com:

Answer 2

console.log(`

     var myStr = 'я! This \\'seems\\' to be a // comment'; // but this is actually the real comment.
    /* like this one */ var butNot = 'this "/*one*/"'; // but this one and /* this one */
    /* and */ var notThis = "one '//but' \\"also\\""; /* // this one */
    `
    
    // 1) replace "/" in quotes with non-printable ASCII '\1' char
    .replace(/("([^\\"]|\\")*")|('([^\\']|\\')*')/g, (m) => m.replace(/\//g, '\1'))
    
    // 2) clear comments
    .replace(/(\/\*[^*]+\*\/)|(\/\/[^\n]+)/g, '')
    
    // 3) restore "/" in quotes
    .replace(/\1/g, '/')

);

Answer 3

If you want to use a RegExp, you could use this one:

/(\/\*[^*]*\*\/)|(\/\/[^*]*)/

This should strip both // ... \n style comments and /* ... */ style comments.

Full working code:

var stringWithoutComments = s.replace(/(\/\*[^*]*\*\/)|(\/\/[^*]*)/g, '');
console.log(stringWithoutComments);

Test with multiline strings:

var s = `before
/* first line of comment
   second line of comment */
after`;
var stringWithoutComments = s.replace(/(\/\*[^*]*\*\/)|(\/\/[^*]*)/g, '');
console.log(stringWithoutComments);

outputs:

before

after