checking if number is even in JavaScript

For the life of me I don't understand why this doesn't work. It looks similar if not identical to many solutions i've seen. Clearly there is something i'm missing. If anyone would care to explain id appreciate it.

var isEven = function(number) {
if (isEven % 2 === 0) {
    return true;
} else {
    return false;
}

};