Assigning a variable a random element from a finite set

Question

In Javascript, how does one declare a variable to be a random element from a predefined finite set of values? For example, suppose a user wants to assign the variable fooBar to be a random element from the set {1, 2, 3}. How would one do this?

Answer 1

From an object:

function pickRandomProperty(obj) {
    var result;
    var count = 0;
    for (var prop in obj)
        if (Math.random() < 1/++count)
           result = prop;
    return result;
}

From an array:

var rand = myArray[Math.floor(Math.random() * myArray.length)];