let userTypes = {};
let keys = Object.keys[userTypes];

error TS2538: Type '{}' cannot be used as an index type.

var a = [1, 2, 3, 4]
console.log(a[{}]);

let keys = Object.keys(userTypes);

let userTypes = {};
let keys = Object.keys[userTypes];

let userTypes = {};
let keys = Object.keys(userTypes);