Programmers frequently need to determine the equality of variables in relation to other variables. This is done using an equality operator.
The most basic equality operator is the == operator. This operator does everything it can to determine if two variables are equal, even if they are not of the same type.
For example, assume:
var foo = 42;
var bar = 42;
var baz = "42";
var qux = "life";foo == bar will evaluate to true and baz == qux will evaluate to false, as one would expect. However, foo == baz will also evaluate to true despite foo and baz being different types. Behind the scenes the == equality operator attempts to force its operands to the same type before determining their equality. This is in contrast to the === equality operator.
The === equality operator determines that two variables are equal if they are of the same type and have the same value. With the same assumptions as before, this means that foo === bar will still evaluate to true, but foo === baz will now evaluate to false. baz === qux will still evaluate to false.