You can use the indexOf method like this:
var index = array.indexOf(item);
if (index !== -1) {
array.splice(index, 1);
}
Note: You'll need to shim it for IE8 and below
var array = [1,2,3,4]
var item = 3
var index = array.indexOf(item);
array.splice(index, 1);
console.log(array)