Akseli Palén Akseli Palén - 2 months ago 7
Javascript Question

How to create a JS object with the default prototype from an object without a prototype?

Background: The module query-string is for example able to parse

key=value&hello=universe
to an object
{key: 'value', hello: 'universe'}
. However, the module author has decided that the returned object does not have a prototype. In other words, this "bastard" object is created by
Object.create(null)
.

Problem: It would be convenient to use
parsed.hasOwnProperty('hello')
but that is not possible without the default object prototype. Of course, one could
Object.prototype.hasOwnProperty.call(parsed, 'hello')
but I think we can all agree that such an expression is kill-immediately-after-birth ugly.

Question: How to nicely convert the prototypeless object to have a default object prototype and methods such as
hasOwnProperty
? Additionally, can this be done without using the feared
__proto__
or
setPrototypeOf
?

Answer

I can't say I've ever done this before, but here's one way to do it

let bastard = Object.create(null);
bastard.father = 'vader';

let adopted = Object.assign({}, bastard);
console.log(adopted.hasOwnProperty('father')); // => true