JavaScript參數傳遞中值和引用的一種理解的詳細介紹

var obj = {};
obj.inner = 10;

var num = 10;
var str = 'Hello';
var boo = true;
var oth = null;
var und = undefined;
var sym = Symbol('foo');

function passingobject(myobj){
 myobj.inner = 1 + myobj.inner ; 
}

function passingvalue(myvalue){
 switch(typeof myvalue){
 case 'number':
 myvalue = myvalue + 1;
 break;
 case 'string':
 myvalue = 'I am a new string now!';
 break;
 case 'boolean':
 myvalue= false;
 break;
 default:
 myvalue = 'Null, Undefined, or Symbol';
 }
 }

 console.log("before num = " + num); // before num = 10
 passingvalue(num);
 console.log("after num = " + num); // after num = 10
 console.log("before str = " + str); // before str = Hello
 passingvalue(str);
 console.log("after str = " + str); // after str = Hello
 console.log("before boo = " + boo); // before boo = true
 passingvalue(boo);
 console.log("after boo = " + boo); // after boo = false
 console.log("before oth = " + oth); // before oth = null
 passingvalue(oth);
 console.log("after oth = " + oth); // after oth = null
 console.log("before und = " + und); // before und = undefined
 passingvalue(und);
 console.log("after und = " + und); // after und = undefined
 console.log(sym); // Symbol(foo)
 passingvalue(sym);
 console.log(sym); // Symbol(foo)
 console.log("before obj.inner = " + obj.inner); // before obj.inner = 10
 passingobject(obj); // after obj.inner = 11
 console.log("after obj.inner = " + obj.inner);

 1 function changeStuff(a, b, c)
 2 {
 3 a = a * 10;
 4 b.item = "changed";
 5 c = {item: "changed"};
 6 }
 7 
 8 var num = 10;
 9 var obj1 = {item: "unchanged"};
10 var obj2 = {item: "unchanged"};
11 
12 console.log(obj1.item); // unchanged
13 console.log(obj2.item); // unchanged
14 changeStuff(num, obj1, obj2);
15 console.log(obj1.item); // changed
16 console.log(obj2.item); // unchanged