A lightweight but safe dictionary, for when Object won't cut it
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An easy but safe string-keyed store

Don't stuff things into objects. Use a dict instead.

The problem

You're probably used to stuffing things into objects:

var hash = {};

hash["foo"] = "bar";

console.log("foo" in hash ? hash["foo"] : "not there"); // "bar"

However this doesn't always work, because your naïve hashes inherit from Object.prototype:

var hash = {};

console.log("hasOwnProperty" in hash); // true!

Even worse, the magic __proto__ property can really ruin your day:

var hash = {};
var anotherObject = { foo: "bar" };

hash["__proto__"] = anotherObject;

console.log("foo" in hash);       // true!!
console.log("__proto__" in hash); // false!!!

Usually you're smart enough to avoid silly key names like "hasOwnProperty", "__proto__", and all the rest. But sometimes you want to store user input in your hashes. Uh-oh…

dict is the solution

Just do an npm install dict and you're good to go:

var dict = require("dict");

var d = dict();

d.set("foo", "bar");
console.log(d.get("foo", "not there")); // "bar"

console.log(d.has("hasOwnProperty")); // false :)

var anotherObject = { baz: "qux" };
d.set("__proto__", anotherObject);
console.log(d.has("baz"));       // false :)
console.log(d.has("__proto__")); // true :)


  • A lightweight ES6-inspired API: get, set, has, delete.
  • get accepts a second argument as a fallback for if the key isn't present (like Mozilla's WeakMap).
  • Doesn't let you get away with being dumb: if you pass a non-string as a key, you're going to get a TypeError.
  • A full suite of unit tests using mocha and chai: npm test awaits you.

See Also

  • rauschma/strmap for something a bit more full-featured (albeit exposing its internals everywhere, if you care about that).
  • dherman/dictjs if you live in an ES6 world.
  • es-lab's StringMap.js if you can deal with the lack of npm support.
  • es6-shim's Map if you want more than just strings for your keys.