How to customize object equality for JavaScript Set

Question

New ES 6 (Harmony) introduces new Set object. Identity algorithm used by Set is similar to === operator and so not much suitable for comparing objects:

Answer 1

Comparing them directly seems not possible, but JSON.stringify works if the keys just were sorted. As I pointed out in a comment

JSON.stringify({a:1, b:2}) !== JSON.stringify({b:2, a:1});

But we can work around that with a custom stringify method. First we write the method

Custom Stringify

Object.prototype.stringifySorted = function(){
    let oldObj = this;
    let obj = (oldObj.length || oldObj.length === 0) ? [] : {};
    for (let key of Object.keys(this).sort((a, b) => a.localeCompare(b))) {
        let type = typeof (oldObj[key])
        if (type === 'object') {
            obj[key] = oldObj[key].stringifySorted();
        } else {
            obj[key] = oldObj[key];
        }
    }
    return JSON.stringify(obj);
}

The Set

Now we use a Set. But we use a Set of Strings instead of objects

let set = new Set()
set.add({a:1, b:2}.stringifySorted());

set.has({b:2, a:1}.stringifySorted());
// returns true

Get all the values

After we created the set and added the values, we can get all values by

let iterator = set.values();
let done = false;
while (!done) {
  let val = iterator.next();

  if (!done) {
    console.log(val.value);
  }
  done = val.done;
}

Here's a link with all in one file http://tpcg.io/FnJg2i