UX Design and Development course

Equality

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.