How to get value from complex object

Question

I'm trying to iterate over p and select a url

p = {
     "photos":[
         {"alt_sizes":[{"url":"img1.png"}]},
         {"alt_sizes":[{"url":"img2.png"}]}
     ]
}

What is the most efficient way to get "url"?

Edit: "photos" can have more than two values, and so I need to iterate

writing an efficient code and making it more efficient by sharing it with community — Ejaz, Apr 23 '13 at 20:03
`p.photos[0].alt_sizes[0];` and `p.photos[1].alt_sizes[0];`. — 11684, Apr 23 '13 at 20:04
The answers so far have all assumed there is only one object with a `url` property in the `alt_sizes` array. Is this the case? — Paul Grime, Apr 23 '13 at 20:10
@PaulGrime yes. also, if anyone was wondering, I'm using the tumblr API — Dann, Apr 23 '13 at 20:13
possible duplicate of [I have a nested data structure / JSON, how can I access a specific value?](http://stackoverflow.com/questions/11922383/i-have-a-nested-data-structure-json-how-can-i-access-a-specific-value) — bfavaretto, Apr 23 '13 at 20:13

Anoop · Accepted Answer · 2013-04-23T20:12:11.107

4

Try this:

function forloop(){
    var arr = p.photos, url , array_of_urls = [];
    for(var i=0; i < arr.length; i++){
       url = arr[i].alt_sizes[0]['url'];
      array_of_urls .push(url);
    }
    console.log(array_of_urls, url)
    return url;
  }

var bigString = "something"+forloop()+"something";

edited Apr 23 '13 at 20:12

answered Apr 23 '13 at 20:05

Anoop

23,044
10
62
76

and how would i go about `return`ing the result? would the normal approach work? – Dann Apr 23 '13 at 20:07
Depends on your application. Return the result to what? – showdev Apr 23 '13 at 20:07
there are multiple url which url you want? – Anoop Apr 23 '13 at 20:07
I have a function that uses a big string that looks something like this: `"something"+forloop+"something"` where forloop is the function described – Dann Apr 23 '13 at 20:10
@Dann Sorry, but what should forloop function return. – Anoop Apr 23 '13 at 20:13
@Sushil this will do, thanks – Dann Apr 23 '13 at 20:17

score 2 · Answer 2 · answered Apr 23 '13 at 20:07

2

Also possible using ECMAScript 5 forEach without the need for an extra library.

var urls = []
p.photos.forEach(function(e) {
    urls.push(e.alt_sizes[0]['url']);
});
console.log(urls);

answered Apr 23 '13 at 20:07

dersvenhesse

6,276
2
32
53

May not need an extra library, but may possibly need a polyfill. Not that that's a bad thing, I'm just saying – Ian Apr 23 '13 at 20:18
Not at all, except IE8 (and older) the support is pretty perfect: http://kangax.github.io/es5-compat-table/#Array.prototype.forEach. – dersvenhesse Apr 23 '13 at 20:21
IE8 and older is still a significant audience...that's my point - I said **may need** – Ian Apr 23 '13 at 20:22

score -1 · Answer 3 · answered Apr 23 '13 at 20:06

-1

Use $.each. An example

 $.each( obj, function( key, value ) {
 alert( key + ": " + value );

  if(typeof(value)=="object")
  {
    $.each( value, function( key, value ) {
         alert( key + ": " + value );
      });
  }
});

answered Apr 23 '13 at 20:06

NullPointerException

3,732
5
28
62

1

why would I need to use jQuery for such a simple end – Dann Apr 23 '13 at 20:09
Because it provides a better way to parse the JSON without worrying about the browser compatibility issues – NullPointerException Apr 23 '13 at 20:10
I second Dann's opinion. That's basic JavaScript. – Florian Salihovic Apr 23 '13 at 20:13
Its choice how you want of go for a solution write something by your own or use something with is existing and tested – NullPointerException Apr 23 '13 at 20:16
@NullPointerException There's no browser compatibility issues you need to worry about with looping over an object/array. Who said this is JSON anyways? There's no parsing in the question – Ian Apr 23 '13 at 20:20
@Ian it is JSON, however that is unimportant as the parsing is done before the snippet in question, and `p` is set as the needed part of said JSON – Dann Apr 23 '13 at 20:37

score -1 · Answer 4 · answered Apr 23 '13 at 20:11

// loop through all properties of `p` (assuming that there might be other objects besides
// `photos` that might have the `url` property we are looking for)
for(i in p){
  // ensure the property is not on the prototype
  if (p.hasOwnProperty(i)) {
    // loop through the array
    for(j = p[i].length; j--;){
      // check that the `url` property is there
      if(typeof p[i][j].alt_sizes[0].url != "undefined"){
        // do something with the url propert - in this case, log to console
        console.log(p[i][j].alt_sizes[0].url)
      }
    }
  }
}

How to get value from complex object

4 Answers4