对象继承
指定哪个对象是新对象的
[[prototype]]
对象字面量隐式指定Object.prototype为其[[prototype]]:
var person = {
name: 'u14e'
};
// 等同于
var person = Object.create(Object.prototype, {
name: {
configurable: true,
enumerable: true,
value: 'u14e',
writable: true,
}
});
var person1 = {
name: 'u14e',
sayName: function() {
alert(this.name);
}
};
var person2 = Object.create(person1, {
name: {
configurable: true,
enumerable: true,
value: 'u148',
writable: true,
}
});
person1.hasOwnProperty('sayName'); // true
person1.isPrototypeOf(person2); // true
person2.hasOwnProperty('sayName'); // false
构造函数继承
创建一个函数时，函数自动生成一个prototype属性，这个属性被自动设置为一个新的继承自Object.prototype的原型对象
function Foo() {}
// js引擎背后设置prototype
Foo.prototype = Object.create(Object.prototype, {
constructor: {
configurable: true,
enumerable: true,
value: Foo,
writable: true,
}
})
function Rectangle(length, width) {
this.length = length;
this.width = width;
}
Rectangle.prototype.getArea = function() {
return this.length * this.width;
};
function Square(size) {
Rectangle.call(this, size, size);
}
Square.prototype = Object.create(Rectangle.prototype, {
constructor: {
configurable: true,
enumerable: true,
value: Square,
writable: true,
}
});
