Function.prototype.toString() now returns exact slices of source code text, including whitespace and comments. Here’s an example comparing the old and the new behavior:

// Note the comment between the `function` keyword
// and the function name, as well as the space following
// the function name.
function /* a comment */ foo () {}

// Previously, in V8:
foo.toString();
// → 'function foo() {}'
//             ^ no comment
//                ^ no space

// Now:
foo.toString();
// → 'function /* comment */ foo () {}'

Feature support #

• Chrome: supported since version 66
• Firefox: supported
• Safari: no support
• Node.js: supported since version 8
• Babel: no support