Eqeqeq

Enforces the use of type-safe equality operators === and !== instead of the more error prone == and != operators.

=== and !== ensure the comparators are of the same type as well as the same value. On the other hand == and != do type coercion before value checking which can lead to unexpected results. For example 5 == "5" is true, while 5 === "5" is false.

Invalid:

if (a == 5) {}
if ("hello world" != input) {}

Valid:

if (a === 5) {}
if ("hello world" !== input) {}