JavaScript object prototype
All JavaScript objects inherit properties and methods from the prototype.
<!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>We also learned that you can not add new attributes to an existing object constructor:
<!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>To add a new constructor property, you must add it to the constructor:
<!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>-
Prototypal inheritance
All JavaScript objects inherit properties and methods from the prototype:
Object.prototype prototype inheritance chain is located at the top: Date Object, Array objects, and Person object inherits from Object.prototype.
- Date object inherits from Date.prototype
- Array object inherits from Array.prototype
- Person object inherits from Person.prototype
Add properties and methods to an object
Sometimes, you want to add a new property (or method) to a given type of all existing objects. Sometimes you want to add a new property (or method) to the object constructor.
Use the prototype property
JavaScript prototype property allows you to add new attributes to the object constructor:
function Person(first, last, age, eyecolor) {
this.firstName = first;
this.lastName = last;
this.age = age;
this.eyeColor = eyecolor;
}
Person.prototype.nationality = "English";JavaScript prototype property also allows you to add new methods to the object constructor:
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;
};