Looping through objects in array

Question

I'm looping trough 2-dimensional objects inside an array. I currently do this the following way:

My array looks like this

var myarray = [
    0: {
          child_obj: {}
       }
    1: {//etc}
];

And I loop through the second-level objects like this

jQuery.each(myarray, function(i, first) {
    jQuery.each(first.child_obj, function(j, second) {
        //do stuff
     }
    });
});

So that's a loop inside a loop. It works fine, but it doesn't look very neat and I feel there might be a better (and shorter) way to do this. The reason I'm doing this is because I need to do stuff with all child_objs.

Worth mentioning:

I use jQuery.each() because this allows looping through objects, while for(), .map() etc. can't handle that properly.
I can't change the structure of the array or its contents
I don't need to use the indexes (args i and j).

Is there a better way?

@user7951676 Could you explain how I should use this to get through the second-level objects? — paddotk
– paddotk, Commented Sep 13, 2017 at 0:43
@JaromandaX I guess you meant var myarray = [].. I edited the question :) — paddotk
– paddotk, Commented Sep 13, 2017 at 0:46
what @user7951676 is trying to say is, that using array forEach for the array is "neater" than jquery each for the array - for the object, you can use jquery each, or Object.keys/Object.values/Object.entries instead if you want to remove all use of jquery — Jaromanda X
– Jaromanda X, Commented Sep 13, 2017 at 0:46

Jaromanda X · Accepted Answer · 2017-09-13 00:59:26Z

1

If you want to ditch jquery (and it's slow speed in .each) and use ES2015+

var myarray = [
    {
        child_obj: {a:1,b:2,c:3}
    },
    {
        child_obj: {a:4,b:5,c:6},
        child_obj2: {a:7,b:8,c:9}
    }
];
// specific rewrite of your code would be
myarray.forEach(obj => Object.values(obj.child_obj).forEach(value => {
    console.log(value);
}));

console.log('-------');
// other examples
myarray.forEach(obj => Object.values(obj).forEach(value => {
    // do things with each "child object"
    console.log(value);
}));

myarray.forEach(obj => Object.values(obj).forEach(child => Object.values(child).forEach(value => {
    // do things with each property in each child object
    console.log(value);
})));

edited Sep 13, 2017 at 0:59

answered Sep 13, 2017 at 0:51

Jaromanda X

1

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1 Comment

paddotk Over a year ago

Not bad, although I'm not sure if this does the right thing for me. Each object has some attributes of which child_obj is just one (maybe should've mentioned that), and it logs for each attribute it loops through. Moreover, if one of these 1st-level attributes have null or undefined value, the loop breaks..

masterpreenz · Accepted Answer · 2017-09-13 00:46:49Z

0

It's not a better way, it's more like alternate.

for (var i = 0; i < myarray.length; i++)
{
  var child_obj = myarray[i].child_obj;
  // get the keys of this object
  var keys = Object.keys(child_obj);

  // loop all those keys
  for (var keyi = 0; keyi < keys.length; keyi++)
  {
    var key  = keys[keyi];
    // get the objects item based on key;
    var item = child_obj[key];
  }
}

but here you can change their values directly as you are iterating the original vars.

hope that helps

answered Sep 13, 2017 at 0:46

masterpreenz

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Comments

OmG · Accepted Answer · 2017-09-13 00:47:26Z

0

using underscore-js library, you can do the following:

var first = _.map(myarray, element => { return element.child_obj; });
_.each(first, element => {/*do stuff*/});

answered Sep 13, 2017 at 0:47

OmG

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1 Comment

paddotk Over a year ago

This doesn't loop through the child objects; if I do something with first.child_obj in the top-level loop, in my jQuery.each, I get the same result.

BSMP · Accepted Answer · 2017-09-13 02:23:42Z

0

You could use forEach with a for in loop inside::

myArray.forEach(function(obj){
for(var i in obj){
// do stuff
}
})

edited Sep 13, 2017 at 2:23

BSMP

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answered Sep 13, 2017 at 0:59

user7951676

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Comments

Slai · Accepted Answer · 2017-09-13 02:40:16Z

0

Naive recursive approach can be used for primitive types:

function forEachPrimitive(o, f, k) { if (o !== Object(o)) f(k, o)
                                     else for (k in o) forEachPrimitive(o[k], f, k) }

var obj = [ { x: { a: '0', b: true, c: 2         } },
            { y: { d: /3/, e: null, f: undefined } } ]

forEachPrimitive(obj, console.log)

answered Sep 13, 2017 at 2:40

Slai

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