Default values for function arguments in javascript.

default_arguments.js

function foo ( red, blue ) {
    // default value for red is true.
    red = typeof red !== 'undefined' ? red : true;

    // default value for blue is 55.
    blue = typeof blue !== 'undefined' ? blue : 55;

    console.log( red );
    console.log( blue );
}

foo( );
foo( false );
foo( true, 100 );