Accessing element of an array in javascript

Question

I want to access an element in an array in javascript without having to do a for loop to access it.

Here's my array:

var array = [{
    "title": "Warnings",
    "numbers": 30,
    "content": [{
        "number": 3001,
        "description": "There may be a problem with the device you are using if you use the default profile"
    }]
}, {
    "title": "Errors",
    "numbers": 20,
    "content": [{
         "number": 1000,
         "description": "No network is loaded"
    }]
}]

I want to access the "content" attribute of "Warnings" without doing a for loop.What I'm currently doing to access it is the following:

var content;
for(a in array) {
    if(a.title == "Warnings") {
        content = a.content;
        break;
    }
}

Is that something feasible in javascript ?

unless you know the specific index of the object you wish to access you are going to have to loop in some manner. Also it is best to use the for(var i = ...) for loop rather than for-in loop. For-in is meant for objects :developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… — scrappedcola
– scrappedcola, Commented Jun 25, 2013 at 18:34
I'm just wondering if there's a built in function or something else in javascript that does this — Etienne Noël
– Etienne Noël, Commented Jun 25, 2013 at 18:35
If there is a function that does this, it will still be looping internally. — Andrew Clark
– Andrew Clark, Commented Jun 25, 2013 at 18:38
if you are using jquery you might look at grep:api.jquery.com/jQuery.grep but as F.J. states it will just be wrapping the for loop in another function and might not be necessarily as efficient as what you already have. — scrappedcola
– scrappedcola, Commented Jun 25, 2013 at 18:38

Mara Ormston · Accepted Answer · 2013-06-25 18:54:36Z

3

Probably the best way to handle this is to change your data to an object instead, and access the object elements by the "title":

var data = {
  "Warnings": {
    "numbers": 30,
    "content": [
      {
        "number" : 3001,
        "description" : "There may be a problem with the device you are using if you use the default profile"
      }
    ]
  },
  "Errors": {
    "numbers": 20,
    "content": [
      {
        "number": 1000,
        "description": "No network is loaded"
      }
    ]
  }
};

Then, you can access the warnings as data.Warnings and the errors as data.Errors.

You can test that they exist with if (data.Warnings) or if (data.Errors) if you don't mind a null failing the test, or if (data.Warnings === undefined) if you'd rather test if the data exists at all.

Using this updated format, to access the content of warnings similar to what you have with '' returned if the data is not available, you would use something like:

var content = data.Warnings ? data.Warnings.content : '';

edited Jun 25, 2013 at 18:54

answered Jun 25, 2013 at 18:38

Mara Ormston

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2 Comments

Bergi Over a year ago

Also notice that with using an object you're loosing their order.

Mara Ormston Over a year ago

@Bergi - If the order matters, and you're trying to access the data quickly (I'm assuming it's significantly more data than the sample and you'll be using it a lot), it is also possible to create an object pointing to the titles with this same method by just assigning each of the titles in that object as the name of each value and having the value as each entry in the original array. I guess that all depends on what the OP is after...

Dmitry Teplyakov · Accepted Answer · 2013-06-25 18:45:18Z

1

var content = ar.filter(function(v) {
    return v.title == 'Warnings';
})[0].content;

answered Jun 25, 2013 at 18:45

Dmitry Teplyakov

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Comments

Martin Lantzsch · Accepted Answer · 2013-06-25 18:35:16Z

0

If you know the index you can simply access it like this:

array[0].content

answered Jun 25, 2013 at 18:35

Martin Lantzsch

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Comments

arifnpm · Accepted Answer · 2013-06-25 19:05:45Z

0

Try using http://jsonselect.org/

you can do what you want using selector:

.title:val("Warnings") ~ .content

answered Jun 25, 2013 at 19:05

arifnpm

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