Is there a simple way to verify that an ES6 Set contains a value that is a particular array? I'd like a solution that doesn't require me to use a reference:
var set = new Set();
var array = [1, 2];
set.add(array);
set.has(array); // true
set.add([3, 4]);
set.has([3, 4]); // false
So far my solution is to store everything as a string, but this is annoying:
set.add([3, 4].toString());
set.has([3, 4].toString()); // true
No there is not.
A Set works on objects and primitives and is useful for preventing identical primitives and re-adding the same object instance.
Each array is their own object, so you can actually add two different arrays with the same values.
var set = new Set();
set.add([3, 4]);
set.add([3, 4]);
console.log(set.size);//2
Additionally, there's nothing to prevent an object from being changed once in a set.
var set = new Set();
var a1 = [3, 4];
var a2 = [3, 4];
set.add(a1);
set.add(a2);
a2.push(5);
for (let a of set) {
console.log(a);
}
//Outputs:
// [3, 4]
// [3, 4, 5]
A set does not have a mechanism for checking the values of objects in a set. Since the value of an object could change at any time, it wouldn't be much more efficient than simply looping over them yourself.
The functionality you are looking for has been kicked around in various ECMAScript proposals:
Record and Tuple (withdrawn at stage 2)
It does not appear to be coming anytime soon.