call javascript object method with a variable

i am new to object oriented javascript. I have a variable whose value i would like to use to call an object's method. like this..

var foo = {
    bar: function() {},
    barr: function() {}
}

now there is a variable whose value can be any of the two method's names bar and barr i want to call them with something like

var myvar = 'bar';
foo.{myVar}();