function say(msg,other,garbage){
alert(arguments[1]);//world
var other = 'nice to meet you!';
var msg;
alert(arguments.length);
alert(msg);//hello
alert(other);//nice to meet you!
alert(arguments[1]);//nice to meet you!
alert(garbage);//undefined
}
say('hello','world');

function say(msg,other,garbage){
//先對(duì)函數(shù)聲明的變量進(jìn)行'預(yù)解析',內(nèi)部執(zhí)行流程，它是是不可見的
var msg = undefined;
var other = undefined;
var garbage = undefined;
//再對(duì)函數(shù)內(nèi)部定義的變量進(jìn)行'預(yù)解析'
var other = undefined;//很明顯，此時(shí)這個(gè)定義已經(jīng)無意義了。
var msg = undefined;//無意義
//對(duì)實(shí)際參數(shù)進(jìn)行賦值操作
msg = new String('hello');//arguments的會(huì)將所有實(shí)際參數(shù)當(dāng)作對(duì)象看待
other = new String('world');
//正式進(jìn)入函數(shù)代碼部分
alert(arguments[1]);//world
other = 'nice to meet you!';
//var msg;這個(gè)已經(jīng)被預(yù)解析了，因此不會(huì)再執(zhí)行
alert(arguments.length);//2
alert(msg);//hello
alert(other);//nice to meet you!
alert(arguments[1]);//nice to meet you!
alert(garbage);//undefined
}