js函數傳參,按值傳遞，按引用傳遞

按值傳遞

函數的形參是所傳實參的拷貝值，形參的值發生改變不會影響實參。

let a=1;
function foo(a){
    a=2;
    console.log(a); // 2
}
foo(a);
console.log(a); // 1
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按引用傳遞

函數的形參是所傳實參的隱式引用，形參的值發生改變會影響實參。

var obj1={name:"lisa"};
 var obj2={name:"jennie"};
function foo(obj){
    obj.name="huahua";
    obj=obj2;
    console.log(obj.name); // jennie
}
foo(obj1);
console.log(obj1.name); // huahua
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棧——> 堆

obj1——> name:"lisa"

obj2——> name:"jennie"

函數執行後

obj/obj1——> name:"huahua"

obj——> name:"jennie"

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js傳參是按值傳遞

function setValue(obj) {
    obj.name = "111";
    var obj = new Object();
    obj.name = "222";
    return obj;
}
let newObj = new Object();
newObj.name = "333";
let result = new setValue(newObj);
console.log(newObj.name); // 111
console.log(result); // {name:"222"}
console.log(result.name); // 222
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