1.直接给对象添加（对象通过字面量创建）
<!DOCTYPE html>
<html>
<body>
<p id="demo"></p>
<script>
var person = {
? firstName: "Bill",
? lastName : "Gates",
? id ? ? : 678,
};
person.name = function() {
? return this.firstName + " " + this.lastName;
};
document.getElementById("demo").innerHTML =
"My friend is " + person.name();?
</script>
</body>
</html>
2. 给对象实例添加（对象通过构造函数new一下创建）
无法为已有的对象构造器添加新属性
例如
Person.nationality = "English";
// Person 对象的构造器函数
function Person(first, last, age, eye) {
? this.firstName = first;
? this.lastName = last;
? this.age = age;
? this.eyeColor = eye;
}
// 创建两个 Person 对象
var myFriend = new Person("Bill", "Gates", 62, "blue");
var myBrother = new Person("Steve", "Jobs", 56, "green");
// 向第一个对象添加 name 方法
myFriend.name = function() {
? return this.firstName + " " + this.lastName;
};
// 显示全名
document.getElementById("demo").innerHTML =
"My friend is " + myFriend.name();?
</script>
3.给对象原型添加
所有 JavaScript 对象都从原型继承属性和方法
使用?prototype?属性
JavaScript prototype 属性允许您为对象构造器添加新属性：
function Person(first, last, age, eyecolor) {
this.firstName = first;
this.lastName = last;
this.age = age;
this.eyeColor = eyecolor;
}
Person.prototype.name = function() {
return this.firstName + " " + this.lastName;
};
给对象添加方法也类似?
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