基于子对象的特定键值以排序顺序迭代 JavaScript 对象 [英] Iterating over a JavaScript object in sort order based on particular key value of a child object

问题描述

短版:我正在寻找 Perl 的 JavaScript 等价物

Short version: I'm looking for the JavaScript equivalent of Perl's

for my $key ( sort { $hash{$a}{foo} cmp $hash{$b}{foo} } keys %hash ) {
    # do something with $key
}

更多细节:

我有一个 JSON 对象，它由一堆具有相同属性的其他 JSON 对象组成，就像 Perl 中的哈希散列:例如:

I have a JSON object which consists of a bunch of other JSON objects which have identical properties to each other, like a hash of hashes in Perl: eg:

var peopleobj = { 
    "0291" : { "Forename" : "Jeremy", "Surname" : "Dyson" },
    "0398" : { "Forename" : "Billy", "Surname" : "Bunter" },
    "6714" : { "Forename" : "Harry", "Surname" : "Peterson" },
    "9080" : { "Forename" : "Barry", "Surname" : "Mainwaring"}
}

我想按姓氏值的顺序遍历 peopleobj 中的对象，例如按姓氏顺序打印出名称.纯 JavaScript 或 jQuery 解决方案将在部署它的上下文中工作.

I want to iterate through the objects in peopleobj in order of the surname values, eg to print out the names in surname order. Plain JavaScript or jQuery solutions will work in the context in which this is being deployed.

提前感谢您的宝贵时间.

Thanks in advance for your valuable time.

推荐答案

有趣的问题...一个简单的 JavaScript 解决方案是根据 'Surname' 在一个单独的数组中为您的对象创建一个索引属性.像这样1:

Interesting question... One plain JavaScript solution is to create an index for your objects in a separate array, based on the 'Surname' property. Something like this¹:

var peopleobj = { 
   "0291" : { "Forename" : "Jeremy", "Surname" : "Dyson" },
   "0398" : { "Forename" : "Billy", "Surname" : "Bunter" },
   "6714" : { "Forename" : "Harry", "Surname" : "Peterson" },
   "9080" : { "Forename" : "Barry", "Surname" : "Mainwaring" }
};

var index = [];

// build the index
for (var x in peopleobj) {
   index.push({ 'key': x, 'Surname': peopleobj[x]['Surname'] });
}

// sort the index
index.sort(function (a, b) { 
   var as = a['Surname'], 
       bs = b['Surname']; 

   return as == bs ? 0 : (as > bs ? 1 : -1); 
}); 

现在你可以遍历你的 index 数组了:

Now you would be able to iterate over your index array:

for (var i = 0; i < index.length; i++) {
   console.log(peopleobj[index[i]['key']]['Surname']);
}

结果(在 Firebug 控制台中测试):

Result (Tested in Firebug console):

Bunter
Dyson
Mainwaring
Peterson

你可能想把它包装成某种可重用的 Iterator 对象，即使它很难像 Perl 一样简洁:

You may want to wrap this up into some sort of reusable Iterator object, even though it would be difficult to get as terse as Perl:

// Our reusable Iterator class:
function MyIterator (o, key) {
   this.index = [];
   this.i = 0;
   this.o = o;

   for (var x in o) {
      this.index.push({ 'key': x, 'order': o[x][key] });
   }

   this.index.sort(function (a, b) { 
      var as = a['order'], 
          bs = b['order']; 

      return as == bs ? 0 : (as > bs ? 1 : -1); 
   }); 

   this.len = this.index.length;
}

MyIterator.prototype.next = function () {
   return this.i < this.len ?
          this.o[this.index[this.i++]['key']] :
          null;
};

然后按如下方式使用:

// Our JavaScript object:
var peopleobj = { 
   "0291" : { "Forename" : "Jeremy", "Surname" : "Dyson" },
   "0398" : { "Forename" : "Billy", "Surname" : "Bunter" },
   "6714" : { "Forename" : "Harry", "Surname" : "Peterson" },
   "9080" : { "Forename" : "Barry", "Surname" : "Mainwaring" }
};

// Build the Iterator object, using the 'Surname' field:
var surnameIter = new MyIterator(peopleobj, 'Surname');

// Iterate:
var i;

while (i = surnameIter.next()) {
   console.log(i['Surname'] + ' ' + i['Forename']);
}

结果:

Bunter Billy
Dyson Jeremy
Mainwaring Barry
Peterson Harry

<小时>

¹ 您可能想要使用 hasOwnProperty() 方法来确保属性属于你的对象而不是继承自 Object.prototype:

for (var x in peopleobj) {
   if (peopleobj.hasOwnProperty(x)) {
      index.push({ 'key': x, 'Surname': peopleobj[x]['Surname'] });
   }
}

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