JavaScript 语言中,编写一个学生类,代码如下：（prototype可以个对象添加属性和方法）
function Student(stuno,stuname) { this.stuno = stuno; this.stuname = stuname; } Student.prototype.stusex = ""; Student.prototype.sayHi = function() { console.log("大家好,我是"+this.stuname+",我的学号是"+this.stuno+",性别:"+this.stusex); } var stu = new Student("001","孙悟空"); stu.stusex = "男"; //或 // var stu = new Student(); // stu.stuno = "001"; // stu.stuname = "孙悟空"; // stu.stusex = "男"; stu.sayHi(); //大家好,我是孙悟空,我的学号是001,性别:男 ES6提供了更接近传统语言的写法,引入了Class这个概念：
constructor为构造函数,当创建对象的时候自动调用：
class Student { constructor(stuno,stuname) { this.stuno = stuno; this.stuname = stuname; } sayHi() { console.log("大家好,我是"+this.stuname+",我的学号是"+this.stuno); } } var stu = new Student("001","孙悟空"); //或 // var stu = new Student(); // stu.stuno = "001"; // stu.stuname = "孙悟空"; stu.sayHi(); //大家好,我是孙悟空,我的学号是001 注意:类的声明第一行除了class Student外,还可以如下写法:
let Student = class let Student = class Student
实例属性和实例方法：
class Student { stuno = ""; stuname = ""; sayHi() //此处方法有的地方称为原型方法 { console.log("大家好,我是"+this.stuname+",我的学号是"+this.stuno); } } var stu = new Student(); stu.stuno = "001"; stu.stuname = "孙悟空"; stu.sayHi(); 静态属性和静态方法：
class Student { stuno = ""; stuname = ""; static proName = ""; //专业名称 static proIntroduce() { console.log("专业名称:"+Student.proName); } sayHi() { console.log("大家好,我是"+this.stuname+",我的学号是"+this.stuno); } } Student.proName = "计算机"; Student.proIntroduce(); class Student { sayHi() { console.log("hi!"); } } let stu = new Student(); stu.sayHi(); 等同于ES5中：
function Student(){ } Student.prototype.sayHi=function() { console.log("hi!"); } var stu = new Student(); stu.sayHi(); class Student { constructor() { this.sayHi = function() { console.log("hi"); } } } let stu = new Student(); stu.sayHi(); 等同于ES5中：
function Student() { this.sayHi = function() { console.log("hi"); } } var stu = new Student(); stu.sayHi(); 当两个方案冲突的时候,constructor里面的函数会覆盖外面的函数：
class Student { sayHi() //等同Student.prototype.sayHi=function(){...} { console.log("hi!"); } constructor() { this.sayHi = function() //等同在function内部定义 { console.log("hello!"); } } } let stu = new Student(); stu.sayHi(); //hello! 等同于ES5中：
function Student() { this.sayHi = function() { console.log("hello!"); } } Student.prototype.sayHi=function() { console.log("hi!"); } var stu = new Student(); stu.sayHi(); //hello! 在类的内部可以使用get和set关键字,对某个属性设置存值函数和取值函数,拦截该属性的存取行为。
class Student { get stuAge(){ return this._stuAge; } set stuAge(age) { if(age >= 18 && age <= 120) this._stuAge = age; else { this._stuAge = 18; console.log("年龄有错误,设置默认值18!"); } } } let stu = new Student(); stu.stuAge = 17; //年龄有错误,设置默认值18! console.log(stu.stuAge); //18 //------------------------------------------------------------------------------ //注意: //(1)在get和set后的属性名不能和函数里的取值和设置值的变量名相同(stuAge和_stuAge) //(2)getter不可单独出现 //(3)getter与setter必须同级出现(不能一个在父类,一个在子类) 通过 extends 实现类的继承。
//通过 extends 实现类的继承。 class People //父类 { name = ""; sex = ""; age = 0; sayHi() { console.log(`姓名:${this.name},性别:${this.sex},年龄:${this.age}`); } } class Student extends People //子类继承父类,拥有父类的属性和方法 { } class Teacher extends People //子类继承父类,拥有父类的属性和方法 { salary = 0; //子类在父类基础上扩展一个属性 sayHi() //子类在父类基础上重写父类方法 { console.log(`姓名:${this.name},性别:${this.sex},年龄:${this.age},月薪:${this.salary}`); } } let stu = new Student(); stu.name = "孙悟空"; stu.sex = "男"; stu.age = 500; stu.sayHi(); //姓名:孙悟空,性别:男,年龄:500 let tc = new Teacher(); tc.name = "唐僧"; tc.sex = "男"; tc.age = 100; tc.salary = 6000; tc.sayHi(); //姓名:唐僧,性别:男,年龄:100,月薪:6000 子类通过super()调用父类构造方法：
class People { constructor(name,sex,age) { this.name = name; this.sex = sex; this.age = age; } sayHi() { console.log(`姓名:${this.name},性别:${this.sex},年龄:${this.age}`); } } class Student extends People { constructor(name,sex,age) { super(name,sex,age); } } class Teacher extends People { constructor(name,sex,age,salary) { super(name,sex,age); this.salary = salary; } sayHi() { console.log(`姓名:${this.name},性别:${this.sex},年龄:${this.age},月薪:${this.salary}`); } } let stu = new Student("孙悟空","男",500); stu.sayHi(); //姓名:孙悟空,性别:男,年龄:500 let tc = new Teacher("唐僧","男",100,6000); tc.sayHi(); //姓名:唐僧,性别:男,年龄:100,月薪:6000 //------------------------------------------------ //注意: //(1)子类 constructor 方法中必须有 super ，且必须出现在 this 之前。 //(2)调用父类构造函数,只能出现在子类的构造函数。 // 例如在sayHi()中调用super就会报错;