Is there any kind of hash code function in JavaScript?

Question

Basically, I\'m trying to create an object of unique objects, a set. I had the brilliant idea of just using a JavaScript object with objects for the property names. Such as,

Answer 1

If you want to have unique values in a lookup object you can do something like this:

Creating a lookup object

var lookup = {};

Setting up the hashcode function

function getHashCode(obj) {
    var hashCode = '';
    if (typeof obj !== 'object')
        return hashCode + obj;
    for (var prop in obj) // No hasOwnProperty needed
        hashCode += prop + getHashCode(obj[prop]); // Add key + value to the result string
    return hashCode;
}

Object

var key = getHashCode({ 1: 3, 3: 7 });
// key = '1337'
lookup[key] = true;

Array

var key = getHashCode([1, 3, 3, 7]);
// key = '01132337'
lookup[key] = true;

Other types

var key = getHashCode('StackOverflow');
// key = 'StackOverflow'
lookup[key] = true;

Final result

{ 1337: true, 01132337: true, StackOverflow: true }

Do note that getHashCode doesn't return any value when the object or array is empty

getHashCode([{},{},{}]);
// '012'
getHashCode([[],[],[]]);
// '012'

This is similar to @ijmacd solution only getHashCode doesn't has the JSON dependency.

Answer 2

Just use hidden secret property with the defineProperty enumerable: false

It work very fast:

• The first read uniqueId: 1,257,500 ops/s
• All others: 309,226,485 ops/s

var nextObjectId = 1
function getNextObjectId() {
    return nextObjectId++
}

var UNIQUE_ID_PROPERTY_NAME = '458d576952bc489ab45e98ac7f296fd9'
function getObjectUniqueId(object) {
    if (object == null) {
        return null
    }

    var id = object[UNIQUE_ID_PROPERTY_NAME]

    if (id != null) {
        return id
    }

    if (Object.isFrozen(object)) {
        return null
    }

    var uniqueId = getNextObjectId()
    Object.defineProperty(object, UNIQUE_ID_PROPERTY_NAME, {
        enumerable: false,
        configurable: false,
        writable: false,
        value: uniqueId,
    })

    return uniqueId
}