access objects stored in an array in Javascript

Question

I am trying to create a new array with just the object values of myArray. My code below returns newArray with both Objects stored, but I am stuck on how to get the 'values' out and put them into the array. I am used to for-in on Objects, but not sure how to access objects when they are stored in an Array.

var myArray = [{first: 'michael', last: 'jordan'}, {first: 'brett', last: 'favre'}];
var myFunc = function (values) {
    newArray = [];
    for (var i = 0; i < values.length; i += 1) {
        newArray.push(values);
    }
    return newArray;
}

What's the expected output? [ 'michael', 'jordan', 'brett', 'favre' ]? — p.s.w.g
– p.s.w.g, Commented Jan 2, 2014 at 3:06

p.s.w.g · Accepted Answer · 2014-01-02 03:11:42Z

4

Try this:

var myFunc = function (values) {
    newArray = [];
    for (var i = 0; i < values.length; i += 1) {
        for(var e in values[i]) {
            newArray.push(values[i][e]);
        }
    }
    return newArray;
}

Demonstration

Note that this method is 'shallow'—that is, it will only get values one-level deep. If you had a structure like [{foo:{bar:'baz'}}], the result would be [{bar:'baz'}].

answered Jan 2, 2014 at 3:11

p.s.w.g

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2 Comments

jstone Over a year ago

I see that working, thank you. Do I always need to write a for-in loop to get access to the objects in an array?

p.s.w.g Over a year ago

@jstone Um no, if you know ahead of time what the properties you want to get are, you could have just done newArray.push(values[i].first, values[i].last) instead of that entire inner loop.

Josh Beam · Accepted Answer · 2014-01-02 03:15:40Z

Consider this example.

var array = ['a','b','c','d'];

The index of 'a' is 0
The index of 'b' is 1
and so forth...

Therefore:

array[0] = 'a'

Next example:

var array = [ { foo: 'bar' }, { hello: 'world' } ];

The index of the first object is 0
The index of the second object is 1

Therefore:

array[0] = { foo: 'bar' }

To access a property of that object, you can do this:

array[0]['foo'] = 'bar';

So, you can do something like this, to iterate over the members of an object, when that object is inside of an array:

var array = [ { foo: 'bar' }, { hello: 'world' } ],
    newArray = [];

var i, len = array.length;

for( i=0; i<len; i++ ) {

    for ( e in array[i] ) {

        newArray.push(array[i][e]);

    }

}

OUTPUT: newArray = ['bar', 'world'];

Ja͢ck · Accepted Answer · 2014-01-02 03:28:40Z

1

This example uses the relatively new Object.keys() and Array.reduce():

var values = myArray.reduce(function(prev, current) {
    return prev.concat(Object.keys(current).map(function(key) { 
        return current[key]; 
    }));
}, []);

answered Jan 2, 2014 at 3:28

Ja͢ck

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