JuniorTheoryCommon

What does the program print?

JavaScript

const key = "a";
const o = { a: 1, key: 2 };
console.log(o.key, o[key]);

2 1

Expecting o.key to use the variable key: after a dot the name is taken literally, so o.key reads the property named key, which is 2.
Expecting o[key] to read the property named key: inside brackets the expression is evaluated first, so o[key] is o["a"], which is 1.

JuniorTheoryCommon

JavaScript

const key = "a";
const o = { a: 1, key: 2 };
console.log(o.key, o[key]);

2 1

Expecting o.key to use the variable key: after a dot the name is taken literally, so o.key reads the property named key, which is 2.
Expecting o[key] to read the property named key: inside brackets the expression is evaluated first, so o[key] is o["a"], which is 1.