json财产价值指数

Question

我需要在一个数组中获取json对象的索引,该数组的对象是id

这是示例代码

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' } }
]

那么伪代码

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

显然这不起作用,但我想知道是否有没有循环找到索引这样做？

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

您可以尝试Array.prototype.map,根据您的示例,它将是:

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

Array.prototype.map在IE7或IE8上不可用.ES5兼容性