Error calling forEach on array

Question

I am getting a problem forEach within anoter forEach function:

The results variable contains an object like:

{
    names: [
        'Someone',
        'Someone else'
    ],
    emails: [
        '[email protected]'
        '[email protected]'
    ]
}

I want it to unwind all the arrays and result in an array like this:

[
    {term: 'Someone', type: 'names'},
    ...
]

Here is my code:

var keys = _.keys(results);

console.log(keys);

var finalResult = [];

keys.forEach( function (key) {

    var arrTerms = results[key];

    console.log(key, arrTerms); //arrTerms prints fine

    arrTerms.forEach(function (term) { //This line throws an exception

        finalResult.push({
            term: term,
            type: key
        });
    });

});

The nested call to forEach throws the following exception:

TypeError: Uncaught error: Cannot call method 'forEach' of undefined

I tried using a for loop with iteration till length, but it generated another exception:

TypeError: Uncaught error: Cannot read property 'length' of undefined

The code as it is works fine for me (except your missing a comma in your array definition). What does results actually look like? — Explosion Pills
– Explosion Pills, Commented Apr 1, 2015 at 15:59

OddDev · Accepted Answer · 2015-04-01 16:10:50Z

1

I think the problem here is that you may assign undefined to your arrTerms (when results[key] returns undefined cause you take a key which isn't contained in your object). Try to do this:

var keys = _.keys(results);

console.log(keys);

var finalResult = [];

keys.forEach( function (key) {
    if(results[key] != undefined){
     var arrTerms = results[key];

     arrTerms.forEach(function (term) { //This line throws an exception
        console.log(key, arrTerms); //arrTerms prints fine
        finalResult.push({
            term: term,
            type: key
        });
     });
    }
});

edited Apr 1, 2015 at 16:10

answered Apr 1, 2015 at 16:06

OddDev

3,7946 gold badges33 silver badges57 bronze badges

Sign up to request clarification or add additional context in comments.

8 Comments

Felix Kling Over a year ago

So, what happens to attTerms if results[key] is undefined?

OddDev Over a year ago

Just nothing. :) We don't want to do anything if we can't find the key, do we?

Felix Kling Over a year ago

But you are still calling arrTerms.forEach even if results[key] is undefined.

OddDev Over a year ago

Oh, overseen that :) ty

Felix Kling Over a year ago

@ZeMoon: _.keys, just like Object.keys, will get all property names of the object. So if you have {foo: undefined}, then you get ['foo']. So it seems, after all, you didn't post the actual structure of the object :P I wonder why didn't catch that, since you called console.log(keys); already.

|

Collectives™ on Stack Overflow

Error calling forEach on array

1 Answer 1

8 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

8 Comments

Your Answer

Sign up or log in

Post as a guest

Related