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In JavaScript, all Objects act a bit like hashmaps. However, the keys to these hashmaps must be strings. If they're not, they're converted with toString() . That means: var a = {foo: 1}; var b = {bar: 2}; var o = {}; o[a] = 100; o[b]; // 100 JSON.stringify(o); // '{"[object Object]":100}' That is, since the toString() of any plain Object is [object Object] , they all address the same value. I'd like to create a hashmap where Objects with the same properties and values address the same value, but objects with different properties or values address different values. That is: var a = {foo: 1}; var b = {bar: 2, baz: 3}; var c = {baz: 3, bar: 2}; var hash = new Hash(); hash.set(a, 100); hash.get(b); // undefined hash.set(b, 200); hash.get(b); // 200 hash.get(c); // 200 My first instinct was to use JSON.stringify() to turn objects into strings, but: var hash = {}; var b = {bar: 2, baz: 3}; var c = {baz: 3, bar: 2}; hash[JSON.stringify(b)] = 100 hash[JSON.stringify(b)] // 100 hash[JSON.stringify(c)] // undefined JSON.stringify(b) // '{"bar":2,"baz":3}' JSON.stringify(c) // '{"baz":3,"bar":2}' That is, JSON serialization is order-dependent. Is there a good library or technique to implement a hashmap like this? Update : Equivalently, is there a good hashing function such that: hash({foo: 1, bar: 2}) == hash({bar: 2, foo: 1})

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