Can I break an _each from inside another _each?

Question

I'm new to underscore. For the outer _each-loop, I wish to count the conversions only once. In other words, I would like it to stop after the first conversion.y++. Is this possible?

_.each(conversions, function(conversion){
 _.each(user.apilog, function(event){
        if( conversion.conditional(event) ){
            conversion.y++;
        }
    })
})

score 2 · Answer 1 · edited May 23 '17 at 11:50

2

Quoting the underscore docs:

It's also good to note that an each loop cannot be broken out of — to break, use _.find instead.

So no, it can't be broken from - their recommendation is to use .find - which breaks on the first truthy value you return from it - that won't help you in nested each though so you can either set a flag:

var flag = false;;
_.find(conversions, function(conversion){
 _.find(user.apilog, function(event){
        if( conversion.conditional(event) ){
            conversion.y++;
            return flag = true;
        }
    });
    return flag;
});

Or not use a nested _.each loop, one elegant approach would be to use a cartesian product:

   var prod = cartProd(conversations, user.apilog);
   _.find(prod, function(item){
        return item[0].conditional(item[1]); // will break on find
   });

Although a plain old JS for loop would also work and would likely be faster.

edited May 23 '17 at 11:50

Community

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1

answered Dec 02 '14 at 21:51

Benjamin Gruenbaum

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Deleting my answer as this is more complete. – Mike Brant Dec 02 '14 at 21:53
nice I was just looking at countBy but as far as I can tell it just put's one item in each group? – Himmators Dec 02 '14 at 21:53
What is your loop actually trying to do? – Benjamin Gruenbaum Dec 02 '14 at 21:54
the `user` has multiple `apilogs`, the idea is to test all `apilog` and if one or more of them is true, increase the value of conversion.y with one. – Himmators Dec 02 '14 at 21:59

Can I break an _each from inside another _each?

1 Answers1