json index of property value

Question

I need to get the index of the json object in an array whose by the objects id

here is the example code

var list = [ { _id: '4dd822c5e8a6c42aa70000ad',
    metadata: 
     { album: 'American IV: Man Comes Around',
       song: 'Hurt',
       coverart: 'http://images.mndigital.com/albums/044/585/435/m.jpeg',
       artist: 'Johnny Cash',
       length: 216,
       mnid: '44585439' } },
  { _id: '4dd80b16e8a6c428a900007d',
    metadata: 
     { album: 'OK Computer (Collector\'s Edition)',
       song: 'Paranoid Android',
       coverart: 'http://images.mndigital.com/albums/026/832/735/m.jpeg',
       artist: 'Radiohead',
       length: 383,
       mnid: '26832739' } },
  { _id: '4dd68694e8a6c42c80000479',
    metadata: 
     { album: 'The Presidents Of The United States Of America: Ten Year Super Bonus Special Anniversary Edition',
       song: 'Lump',
       coverart: 'http://images.mndigital.com/albums/011/698/433/m.jpeg',
       artist: 'The Presidents Of The United States Of America',
       length: 134,
       mnid: '11698479' } }
]

then pseudo code

 var index_of  = list.indexOf("4dd80b16e8a6c428a900007d");

obviously that is not gonna work but I wonder if there is anyway to do this without looping to find the index ?

Answer 1

var i = list.length;
while( i-- ) {
    if( list[i]._id === '4dd80b16e8a6c428a900007d' ) break;
}

alert(i);  // will be -1 if no match was found

Answer 2

You can try Array.prototype.map, based on your example it will be:

var index = list.map(function(e) { return e._id; }).indexOf('4dd822c5e8a6c42aa70000ad');

Array.prototype.map is not available on IE7 or IE8. ES5 Compatibility