关于js函数的形参和实参

window.onload = function(){
function dada(name){
alert(arguments.length);//获取实际被传递参数的数值。实参  //3
alert(dada.length);// // 获取期望参数的数值，函数定义时的预期参数个数，形参  //1
alert("i'm " + name + arguments[1] + " years old." + "i'm in " + arguments[2] );//name等于arguments[0]  im jiangsen 23 years old im in chengdu
}
dada("jiangsen",23,"chengdu")
}