How to Sort a JS Object Literal?

Turns out object property order is predictable since ES2015. Which is amazing.

Check it out here.

Re: How to sort a JS Object?

Answer: You can't. So instead, you need a more sophisticated data structure. You have many options:

1. You can use a separate array to hold the order of the object's keys. (This is what @Felix Kling's answer demonstrates.) Good: fast retrieval via order or name. Bad: needs a second data structure that must be kept synched with the first.
2. Instead of the Object simply holding properties and values, the properties could hold Objects which hold the values and a sort order. Good: 1 data structure. Fast lookup by property name. Bad: slow lookup by order (need to scan the structure). Slow sorting.
3. Use an array, with elements consisting of Objects that hold the key and the value. Good: 1 data structure. Fast lookup by order. Fast sorting. Bad: slow lookup by property name (need to scan the structure).

I recommend solution 3 since it uses the JS mechanics to manage the ordering.

Examples:

// Object holds sort order:  (Solution 2)
var foo = {
  Suzy: {v: 4, order: 0},
  Billy: {v: 5, order: 1},
  Jimmy: {v: 2, order: 2},
  Sally: {v: 1, order: 3}
};    

// Array holds keys: (Solution 3)
var woof = [
  {k: 'Suzy', v: 4},
  {k: 'Billy', v: 5},
  {k: 'Jimmy', v: 2},
  {k: 'Sally', v: 1}
];

// Sort the woof array by the key names:
woof.sort(function(a, b) {
  return a.k.localeCompare(b.k);
});

// The third key and value:
woof[2].k; // the third key
woof[2].v; // the third value

Edited: updated code to fix typo. Thank you, @Martin Fido

Object properties are in no specific order (the order is implementation dependent) and you cannot sort the properties.

You have to keep an array of keys and sort it accordingly, for example:

var keys = [];

for(var key in obj) {
    if(obj.hasOwnProperty(key)) {
        keys.push(key);
    }
}

keys.sort(function(a, b) {
    return obj[a] - obj[b];
});

Now you can iterate over the values of the array and use them to access the corresponding property of the object.