es-hash

Small library to create hashes from objects

This is a small module to create hashes from simple objects. The ECMA Standart defines Javascript Objects as unordered, so you can't just iterate over the object and save a hash for each key value pair, you have to sort it. This module does that for you so you can easily compare objects that have identical content but are ordered differently.

Example

var hash = require('es-hash');
 
// Create two objects with identical content in a different order 
var obj1 = { bla: 'blub', blub: 'bla' },
    obj2 = { blub: 'bla', bla: 'blub' };
 
// Compare the hashes 
console.log('Obj1 - ' + hash(obj1));
console.log('Obj2 - ' + hash(obj2));

Using Objects as Array keys

You may face the problem that array keys in javascript are always strings. So if you use an object as key, the resulting key will be [object Object]. Thats not what we intended to do, as you can see in the following example.

var foo = {};
 
foo[{bar: 'foo'}] = 'foo';
 
/*
 * Expected output:
 *  foo
 *  undefined
 *
 * Actual output:
 *  foo
 *  foo
 */
console.log(foo[{bar: 'foo'}]);
console.log(foo[{}]);

You can still use the same syntax if you just override Object.toString and return a hash for the current object.

var hash = require('es-hash');
 
// Save data in an object with an object as a key 
Object.prototype.toString = function () {
    return '[object Object #'+hash(this)+']';
}
 
var foo = {};
 
foo[{bar: 'foo'}] = 'foo';
 
/*
 * Output:
 *  foo
 *  undefined
 */
console.log(foo[{bar: 'foo'}]);
console.log(foo[{}]);

Running Tests

$ nodeunit test.js