Method overloading in Javascript

JavaScript does not support method overloading (as in Java or similiar), your third function overwrites the previous declarations.

Instead, it supports variable arguments via the arguments object. You could do

function somefunction(a, b) {
    if (arguments.length == 0) { // a, b are undefined
        // 1st body
    } else if (arguments.length == 1) { // b is undefined
        // 2nd body
    } else if (arguments.length == 2) { // both have values
        // 3rd body
    } // else throw new SyntaxError?
}

You also could just check for typeof a == "undefined" etc, this would allow calling somefunction(undefined), where arguments.length is 1. This might allow easer calling with various parameters, e.g. when you have possibly-empty variables.