JavaScript prototype原型用法
程序员文章站
2024-01-01 16:21:28
JavaScript prototype原型用法,所有JavaScript对象都从原型继承属性和方法。 ......
javascript对象原型
所有javascript对象都从原型继承属性和方法。
<!doctype html>
<html>
<meta charset="utf-8">
<title>js</title>
<body>
<h2>javascript 对象</h2>
<p id="demo"></p>
<script>
function person(first, last, age, eye) {
this.firstname = first;
this.lastname = last;
this.age = age;
this.eyecolor = eye;
}
var myfather = new person("john", "doe", 50, "blue");
var mymother = new person("sally", "rally", 48, "green");
document.getelementbyid("demo").innerhtml =
"my father is " + myfather.age + ". my mother is " + mymother.age;
</script>
</body>
</html>
我们还了解到，您无法向现有对象构造函数添加新属性：
<!doctype html>
<html>
<meta charset="utf-8">
<title>javascript对象</title>
<body>
<h2>javascript对象</h2>
<p>您无法向构造函数添加新属性。</p>
<p id="demo"></p>
<script>
function person(first, last, age, eye) {
this.firstname = first;
this.lastname = last;
this.age = age;
this.eyecolor = eye;
}
person.nationality = "english";
var myfather = new person("john", "doe", 50, "blue");
var mymother = new person("sally", "rally", 48, "green");
document.getelementbyid("demo").innerhtml =
"the nationality of my father is " + myfather.nationality;
</script>
</body>
</html>
要向构造函数添加新属性，必须将其添加到构造函数：
<!doctype html>
<html>
<meta charset="utf-8">
<title>javascript对象</title>
<body>
<h2> javascript对象</h2>
<p id="demo"></p>
<script>
function person(first, last, age, eye) {
this.firstname = first;
this.lastname = last;
this.age = age;
this.eyecolor = eye;
this.nationality = "english";
}
var myfather = new person("john", "doe", 50, "blue");
var mymother = new person("sally", "rally", 48, "green");
document.getelementbyid("demo").innerhtml =
"我父亲的国籍是 " + myfather.nationality + ". 我母亲的国籍是： " + mymother.nationality;
</script>
</body>
</html>
原型继承
所有javascript对象都从原型继承属性和方法：
object.prototype位于原型继承链的顶部：date对象，array对象和person对象继承自object.prototype。
* date 对象继承自 date.prototype
* array 对象继承自 array.prototype
* person 对象继承自 person.prototype
# 向对象添加属性和方法
有时，您希望向给定类型的所有现有对象添加新属性（或方法）。有时您想要向对象构造函数添加新属性（或方法）。
使用**原型**属性
javascript prototype属性允许您向对象构造函数添加新属性：
function person(first, last, age, eyecolor) {
this.firstname = first;
this.lastname = last;
this.age = age;
this.eyecolor = eyecolor;
}
person.prototype.nationality = "english";
javascript prototype属性还允许您向对象构造函数添加新方法：
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;
};
推荐阅读