angular filter empty array in an object

Question

I have this array of objects

var list = [{
    "questionId": 1,
    "correctChoiceIds": [],
    "choiceId": 0,
    "number": 1
}, {
    "questionId": 1,
    "correctChoiceIds": [1234, 4567],
    "choiceId": 0,
    "number": 2,
}, {
    "questionId": 2,
    "correctChoiceIds": [],
    "choiceId": 0,
    "number": 3
}];

//This filter gives me an array with list[0] and list[1]
var filterQuestion = $filter('filter')(list, { questionId: 1 }, true);

I want to filter all those with an empty array for their correctChoiceIds.

var filterNoCorrectChoice= $filter('filter')(list, { correctChoiceIds: [] }, true);

This is what I came up with but it simply gives me nothing. I'm not sure if this is the right way or why it results to nothing.

Muhammad Abid · Accepted Answer · 2016-04-04 05:39:02Z

2

see demo

Use the filter like this,

  var filterNoCorrectChoice= $filter('filter')(list,function(item) {
        // must have array, and array must be empty
        return item.correctChoiceIds && item.correctChoiceIds.length === 0;
    });

answered Apr 4, 2016 at 5:39

Muhammad Abid

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Comments

Juan Pablo · Accepted Answer · 2016-04-04 05:39:51Z

0

method filter native

var filterQuestion = list.filter(function(el){ return el.correctChoiceIds.length<1; });
// result
console.log(filterQuestion);

answered Apr 4, 2016 at 5:39

Juan Pablo

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Comments

Kutyel · Accepted Answer · 2016-04-04 05:57:07Z

0

I want to filter all those with an empty array for their correctChoiceIds

You don't need an angular filter for that, use a standard, native javascript filter...

list.filter(x => !x.correctChoiceIds.length);

answered Apr 4, 2016 at 5:57

Kutyel

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2 Comments

riyu Over a year ago

This one also works but I don't understand quite understand the syntax. I am still a beginner.

Kutyel Over a year ago

@riyu you can have a look at the docs for filter and for arrow functions as well, but basically you are filtering all the items in your list which have an empty correctChoiceIds array (x.correctChoiceIds.length === 0, 0 is a falsy value in javascript, that's why I negate the condition with the !). Hope now it is more clear ;)

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