how to stop Javascript forEach? [duplicate]

Question

I'm playing with Node.js and Mongoose — trying to find specific comment in deep comments nesting with recursive function and forEach within. Is there a way to stop Node.js forEach? As I understand every forEach iteration is a function and and I can't just do break, only return but this won't stop forEach.

function recurs(comment) {     comment.comments.forEach(function(elem) {          recurs(elem);          //if(...) break;      }); } 

Answer 1

You can't break from a forEach. I can think of three ways to fake it, though.

1. The Ugly Way: pass a second argument to forEach to use as context, and store a boolean in there, then use an if. This looks awful.

2. The Controversial Way: surround the whole thing in a try-catch block and throw an exception when you want to break. This looks pretty bad and may affect performance, but can be encapsulated.

3. The Fun Way: use every().

['a', 'b', 'c'].every(function(element, index) {   // Do your thing, then:   if (you_want_to_break) return false   else return true }) 

You can use some() instead, if you'd rather return true to break.

Answer 2

Breaking out of Array#forEach is not possible. (You can inspect the source code that implements it in Firefox on the linked page, to confirm this.)

Instead you should use a normal for loop:

function recurs(comment) {     for (var i = 0; i < comment.comments.length; ++i) {         var subComment = comment.comments[i];         recurs(subComment);         if (...) {             break;         }     } } 

(or, if you want to be a little more clever about it and comment.comments[i] is always an object:)

function recurs(comment) {     for (var i = 0, subComment; subComment = comment.comments[i]; ++i) {         recurs(subComment);         if (...) {             break;         }     } }