What is the time complexity of javascript's array.indexOf?

Question

Does indexOf simply walk through the array or does it do something that is faster? I know that this is implementation dependent but what does Chrome or Firefox do?

Answer 1

In ECMA6, you have the Set(), and then you can do:

var obj = new Set();
obj.add(1);
obj.has(1) === true;
obj.has(2) === false;

The performance of has is O(1).