JS - 对象(4)

属性标签

属性级的权限设置

查看对象上的属性标签

Object.getOwnPropertyDescriptor({
    pro: true
}, 'pro');
// 可写，修改； 可枚举； 可删除
// Object {value: true, writable: true, enumerable: true, configurable: true}
Object.getOwnPropertyDescriptor({
    pro: true
}, 'a'); // undefined

var person = {};
Object.defineProperty(person, 'name', {
    configurable: false,
    writable: false,
    enumerable: true,
    value: 'sunorry'
});

person.name; // sunorry
person.name = 1;
person.name; //still sunorry
delete person.name; //false

Object.defineProperty(person, 'type', {
    configurable: true,
    writable: true,
    enumerable: false,
    value: 'Object'
});

// 返回对象的key
Object.keys(person); // ['name']， type不可枚举

实际一点的例子

//默认 false
Object.defineProperties(person, {
    title: {value: 'fe', enumerable: true},
    corp: {value: 'Qunar', enumerable: true},
    salary: {value: 1000, enumerable: true, writable: true}
});

Object.getOwnPropertyDescriptor(person, 'salary');
// Object {value, 1000, writeable: true, enumerable: true, configurable: false}
Object.getOwnPropertyDescriptor(person, 'corp');
// Object {value, 'Qunar', writeable: false, enumerable: true, configurable: false}

复杂点

Object.defineProperties(person, {
    title: {value: 'fe', enumerable: true},
    corp: {value: 'Qunar', enumerable: true},
    salary: {value: 1000, enumerable: true, writable: true},
    luck: {
        get: function () {
            return Math.random() > 0.5 ? 'good' : 'bad';
        }
    },
    promote: {
        set: function(level) {
            this.salary *= 1 + level * 0.1
        }
    }
});

Object.getOwnPropertyDescriptor(person, 'salary');
// Object {value, 1000, writeable: true, enumerable: true, configurable: false}
Object.getOwnPropertyDescriptor(person, 'corp');
// Object {value, 'Qunar', writeable: false, enumerable: true, configurable: false}

person.salary; // 1000
person.promote = 2;
person.salary; // 1200

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