按underscore.js中的键排序

Question

I have one dictionary:

{
    abc : {id : 1},
    defg : {id : 2}
}

I want to sort dictionary by keys length using underscore.js Output like:

{
    defg : {id : 2},
    abc : {id : 1}
}

Prototype work: http://jsfiddle.net/UCWL2/71/

Answer 1

Dictionary, which is a plain JS object, can't be reliably sorted, because the order of elements isn't specified by the ECMA Script 5 spec. Of course, you might rely on the browser-specific behaviour, but that isn't guaranteed to be the same accross browsers, their versions etc.

If you need sorted maps, you'd want to use arrays (but then you lose the log(n) access complexity), or some 3rd party library for that (ie dsjslib ).

Answer 2

var avatars = [
    {idx: 102, userInfo: {buddy_name: 'Avatar102', is_online: 1}},
    {idx: 100, userInfo: {buddy_name: 'Avatar100', is_online: 1}},
    {idx: 101, userInfo: {buddy_name: 'Avatar101', is_online: 1}}
];

avatars = _(avatars).sortBy(function(avatar) {
    return -avatar.idx;// -ve is put in front of variable to sort in desc i.e reverse direction
});
console.log(JSON.stringify(avatars));

Just replace return avatar.idx;//.userInfo.buddy_name; by return -avatar.idx;//.userInfo.buddy_name; it reverses the result.

Working jsfiddle : http://jsfiddle.net/0Lb44h96/