Array.find() versus Object.key access

Question

I'm curious how accessing object keys in JavaScript works "under the hood" — when you key an object, does it loop through all of its keys (.find style) until it locates one that matches your accessor? Or does it have some faster way of finding the value corresponding to a key? As an illustration, say you have an object and an array like so:

const arr = ["a","b","c"];
const obj = {"i0":"a","i1":"b","i2":"c"};

In this circumstance, would it be faster to look up obj.i1, or arr.find(a=>a=="b")?