迭代基於子對象的特定鍵值

Question

短版的排序順序JavaScript對象：我在尋找的JavaScript相當於Perl的

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

更多細節：

我有一個JSON對象其由一串具有相同的性質彼此，像散列在Perl的散列其他JSON對象中的：例如：

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

我想通過對象來迭代我ñpeopleobj按姓氏的順序，例如按姓氏順序打印姓名。普通的JavaScript或jQuery解決方案將在正在部署的環境中工作。

在此先感謝您寶貴的時間。

Answer 1

有趣的問題...一個普通的JavaScript解決方案是基於'Surname'屬性在單獨的數組中創建對象的索引。事情是這樣的：

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); 
}); 

現在你就可以在你的index數組遍歷：

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

結果（在Firebug控制檯測試）：

Bunter 
Dyson 
Mainwaring 
Peterson 

您可能想要將其包裝成某種可重用的Iterator對象，儘管它很難像Perl那樣簡潔：

// 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; 
}; 

然後按如下方式使用它：

// 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']); 
} 

結果：

Bunter Billy 
Dyson Jeremy 
Mainwaring Barry 
Peterson Harry 

---

您可能需要使用hasOwnProperty()方法，以確保財產屬於您的對象，而不是從Object.prototype繼承：

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