1、js为什么要构造函数
使用构造函数构造可以复用的对象
构造函数就是你构造出来的函数,是一种特殊的方法,与普通函数有着质的区别,其作用,在创建对象的时候主要用来初始化对象,就是给对象成员赋初始值,构造函数的主要特征就是方法名、首字母大写,并且用new来使用
2、ES5
function foo(){
this.name = 'Katherine';
this.age = '26';
}
var f = new foo();
console.log(f) //Object
console.log(f.name) //Katherine
console.log(f.age) //26
function foos(name,age,sex){
this.name = name;
this.age = age;
this.sex = sex;
}
var f1 = new foos('Kathrine', '26', 'female');
var f2 = new foos('Stefan', '27', 'male');
var f3 = new foos('Damon', '29', 'male');
console.log(f1) //foos {name: "Kathrine", age: "26", sex: "female"}
console.log(f2) //foos {name: "Stefan", age: "27", sex: "male"}
console.log(f3) //foos {name: "Damon", age: "29", sex: "male"}
3、ES6
class foo{
constructor(){
this.name = 'Karherine';
this.age = '26';
}
vampire(va){
console.log('Her name is '+this.name+' and she was '+this.age+' years old')
}
}
let f = new foo()
f.vampire(); //Her name is Karherine and she was 26 years old
//继承原型
class foos extends foo{
constructor(){
super();
this.name = 'Stefan';
this.age = '27';
}
}
let f1 = new foos();
f1.vampire(); //His name is Stefan and he was 27 years old
1、ES5可以用new生成对象,也可以直接调用构造函数,直接调用当成普通函数使用。比如函数foo();
2、ES6必须用new生成对象,不可以直接调用构造函数成普通函数使用。