Loop through an object of objects with arrays as values

Question

So I have an object like this:

{
  "apples": [
    "one",
    "two"
  ],
  "oranges": [
    "three",
    "four"
  ]
}

How do I look through this object and find four for example? Something like:

for (var i=0; i < obj.length; i++) {
  for (var y=0; y <obj.childObj.length; y++ {
    obj.childObj[i] === 'four' ? return : null;
  }
}

Or is there a better way to structure this data?

Your code is wrong. `return` cannot be used like that. what is your requirement. — Rajaprabhu Aravindasamy, Apr 13 '16 at 09:48
it depends on the purpose. if you always search for four, then an object with a key four would make sense. — Nina Scholz, Apr 13 '16 at 09:49
Don't use same variable in nested loops for iteration in your case `i`; — itzmukeshy7, Apr 13 '16 at 09:51
Structure as you want (if you are looking for values that are not unique and good enough to be used as hashmap keys), you are going through all the elements one by one. — Mike B, Apr 13 '16 at 09:53

Aditya · Accepted Answer · 2016-04-13T09:55:41.487

2

for(var x in obj)
 if(obj.hasOwnProperty(x)) {
  for(var y in obj[x])
   if(obj[x].hasOwnProperty(y)) {
    obj[x][y] === 'four' ? doSomething() : doSomethingElse();
   }
  }

EDIT : Improvement as suggested by Matthew Herbst

edited Apr 13 '16 at 09:55

answered Apr 13 '16 at 09:49

Aditya

80
6

Looks good initially. Is this the most efficient way to store and retrieve multi-dimensional information like this though? – j_d Apr 13 '16 at 09:51
2

Make sure to also use `obj.hasOwnProperty(x)` and `obj[x].hasOwnProperty(y)` – Matthew Herbst Apr 13 '16 at 09:51
I'm not aware of any other way which could give you a significant performance boost over this one. – Aditya Apr 13 '16 at 09:53
What is the benefit of hasOwnProperty? – j_d Apr 13 '16 at 09:57
@JohnDoe It'll check only for the own properties and not for the inherited properties. See [hasOwnProperty](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty) Also see [this SO post](http://stackoverflow.com/questions/2600085/hasownproperty-in-javascript) – Tushar Apr 13 '16 at 09:58
The check prevents inherit properties from being iterated over, If there are any. If you have an object that inherits too many properties and you don't want them being iterated over, Object.keys could be a better alternative. – Aditya Apr 13 '16 at 10:03

score 0 · Answer 2 · answered Apr 13 '16 at 09:52

You can use for (x in y) statemment:

var data = {
  "apples": [
    "one",
    "two"
  ],
  "oranges": [
    "three",
    "four"
  ]
};

for (var key in data) {
    var obj = data[key];
    for (var i=0; i <obj.length; i++) {
        // obj[i] === 'four' ? return : null;
        console.log(obj[i]);
    }
}

This will print:

one
two
three
four

score 0 · Answer 3 · answered Apr 13 '16 at 09:54

If you want to find out if this object has four somewhere then

var isFourAvailable = Object.keys(obj).filter(function(val){ return obj[val].indexOf("four") != -1 }).length > 0;

Making it more generic

function findX(x)
{
   return Object.keys(obj).filter(function(val){ return obj[val].indexOf(x) != -1 }).length > 0;
}

score 0 · Answer 4 · answered Apr 13 '16 at 09:55

0

Try this ;)

Modified your code;

for (var i = 0; i < obj.length; i++) {
  for (var y = 0; y < obj[i].length; y++ {
    if(obj[i][y] === 'four'){
      console.log("It's four");
    }
  }
}

answered Apr 13 '16 at 09:55

itzmukeshy7

2,669
1
21
29

score 0 · Answer 5 · answered Apr 13 '16 at 09:56

You can use indexOf

   var x={
      "apples": [
        "one",
        "two"
      ],
      "oranges": [
        "three",
        "four"
      ]
    }
    for (var e in x) {
      if (x[e].indexOf("four") > -1)
        console.log("found Four");
    }

Loop through an object of objects with arrays as values

5 Answers5