alertX in $.proxy(alertX,o) is without braces (the braces will end up calling the function).
var o = {'x':6};
var x = 9;
function alertX() {
alert(this.x);
}
//use proxy so that calling alertX() will alert the value
// of o.x (currently 6), not x in the global scope (currently 9)
var $proxiedAlertX = function(){
$.proxy(alertX,o);
}
$proxiedAlertX()