in javascript, is there an easy way to sort key-value pairs by the value, and return the key?

In javascript, is开发者_运维百科 there an easy way to sort key-value pairs by the value (assume the value is numeric), and return the key? A jQuery way to do this would be useful as well.

(There are a lot of related questions about key-value pairs here, but I can't find one specifically about sorting.)

---

There's nothing easy to do this cross-browser. Assuming an array such as

var a = [
    {key: "foo", value: 10},
    {key: "bar", value: 1},
    {key: "baz", value: 5}
];

... you can get an array of the key properties sorted by value as follows:

var sorted = a.slice(0).sort(function(a, b) {
   return a.value - b.value;
});

var keys = [];
for (var i = 0, len = sorted.length; i < len; ++i) {
    keys[i] = sorted[i].key;
}

// keys is ["bar", "baz", "foo"];

---

Let's assume we have an Array of Objects, like:

var data = [
    {foo: 6},
    {foo: 2},
    {foo: 13},
    {foo: 8}
];

We can call Array.prototype.sort()^help, use Array.prototype.map()^help to map a new array and Object.keys()^help to grab the key:

var keys = data.sort(function(a,b) {
    return a.foo - b.foo;
}).map(function(elem, index, arr) {
   return Object.keys(elem)[0];
});

Be aware of, Array.prototype.map() requires Javascript 1.6 and Object.keys() is ECMAscript5 (requires Javascript 1.8.5).

You'll find alternative code for all those methods on MDC.

---

As far as I know, there isn't a built-in Javascript function to sort an array by its keys.

However, it shouldn't take too much code to do it: just extract the keys into their own array, sort them using the normal sort function, and rebuild the array in the right order. Something like this should do the trick:

function SortArrayByKeys(inputarray) {
  var arraykeys=[];
  for(var k in inputarray) {arraykeys.push(k);}
  arraykeys.sort();

  var outputarray=[];
  for(var i=0; i<arraykeys.length; i++) {
      outputarray[arraykeys[i]]=inputarray[arraykeys[i]];
  }
  return outputarray;
}

Now you can just call your function like so:

var myarray = {'eee':12, 'blah':34 'what'=>66, 'spoon':11, 'snarglies':22};
myarray = SortArrayByKeys(myarray);

And the output will be:

{'blah':34, 'eee':12, 'spoon':11, 'snarglies':22, 'what':66}

Hope that helps.

Working test page here: http://jsfiddle.net/6Ev3S/

---

Given

var object = {
  'a': 5,
  'b': 11,
  'c': 1,
  'd': 2,
  'e': 6
}

You can sort object's keys by their values using the following:

Object.keys(object).sort(function (a, b) {
  return object[a] - object[b]
}))

Result

[ 'c', 'd', 'a', 'e', 'b' ]

---

If you can't count on the exended array and object properties,

you can use the original Array methods-

function keysbyValue(O){
    var A= [];
    for(var p in O){
        if(O.hasOwnProperty(p)) A.push([p, O[p]]);
    }
    A.sort(function(a, b){
        var a1= a[1], b1= b[1];
        return a1-b1;
    });
    for(var i= 0, L= A.length; i<L; i++){
        A[i]= A[i][0];
    }
    return A;
}
//test

    var Obj={a: 20, b: 2, c: 100, d: 10, e: -10};
    keysbyValue(Obj)

    /*  returned value: (Array)
    e,b,d,a,c
    */