[Day26] 求值策略

• Call by Value 传值
• Call by Reterence 传参照
• Call by Sharing

JavaScript 的纯值为传值，物件为传参照

Call by Value 传值

var num = 1;
var str = '一';

var num2 = num;
var str2 = str;

num2 = 2;
str = '二';

console.log(num, num2); // 1 2
console.log(str, str2); // 一 二

Call by Reterence 传参照

var person = {
    name: 'Carol',
    age: 18
};

var person2 = person;

console.log(person); // {name: 'Carol', age: 20}
console.log(person2); // {name: 'Carol', age: 20}

Call by Sharing 传共用物件

function fn(person) {
    person.age = 20;
    person = {
        name: 'Mary',
    };
    return person;
}

var person = {
    name: 'Carol',
    age: 18
};

var person2 = fn(person);

console.log(person); // {name: 'Carol', age: 20}
console.log(person2); // {name: 'Mary'}

var person = {
    name: 'Carol',
    age: 18
};

var person2 = person;

person.age = 20;
person = {
    name: 'Mary',
};

console.log(person); // {name: 'Mary'}
console.log(person2); // {name: 'Carol', age: 20}