How do I check if an array includes a value in JavaScript?

What is the most concise and efficient way to find out if
a JavaScript array contains a value?

This is the
only way I know to do it:

function
            contains(a, obj) {
 for (var i = 0; i < a.length; i++) {
 if
            (a[i] === obj) {

 return true;
 }
 }

            return
            false;
}

Is
there a better and more concise way to accomplish
this?

This is very closely related to question
href="https://stackoverflow.com/questions/143847/best-way-to-find-an-item-in-a-javascript-array">Best
way to find an item in a JavaScript Array? which addresses finding
objects in an array using indexOf.