题目描述：
ES5/ES6 的继承除了写法以外还有什么区别？
解题：
const bar = new Bar(); // it's ok
function Bar() {
this.bar = 42;
}
const foo = new Foo(); // ReferenceError: Foo is not defined
class Foo {
constructor() {
this.foo = 42;
}
}
// 引用一个未声明的变量
function Bar() {
baz = 42; // it's ok
}
const bar = new Bar();
class Foo {
constructor() {
fol = 42; // ReferenceError: fol is not defined
}
}
const foo = new Foo();
- 3.class 的所有方法（包括静态方法和实例方法）都是不可枚举的。
// 引用一个未声明的变量
function Bar() {
this.bar = 42;
}
Bar.answer = function() {
return 42;
};
Bar.prototype.print = function() {
console.log(this.bar);
};
const barKeys = Object.keys(Bar); // ['answer']
const barProtoKeys = Object.keys(Bar.prototype); // ['print']
class Foo {
constructor() {
this.foo = 42;
}
static answer() {
return 42;
}
print() {
console.log(this.foo);
}
}
const fooKeys = Object.keys(Foo); // []
const fooProtoKeys = Object.keys(Foo.prototype); // []
- 4.class 的所有方法（包括静态方法和实例方法）都没有原型对象 prototype，所以也没有[[construct]]，不能使用 new 来调用。
function Bar() {
this.bar = 42;
}
Bar.prototype.print = function() {
console.log(this.bar);
};
const bar = new Bar();
const barPrint = new bar.print(); // it's ok
class Foo {
constructor() {
this.foo = 42;
}
print() {
console.log(this.foo);
}
}
const foo = new Foo();
const fooPrint = new foo.print(); // TypeError: foo.print is not a constructor
function Bar() {
this.bar = 42;
}
const bar = Bar(); // it's ok
class Foo {
constructor() {
this.foo = 42;
}
}
const foo = Foo(); // TypeError: Class constructor Foo cannot be invoked without 'new'
- 6.class 内部无法重写类名。 ```javascript function Bar() { Bar = ‘Baz’; // it’s ok this.bar = 42; } const bar = new Bar(); // Bar: ‘Baz’ // bar: Bar {bar: 42}
class Foo { constructor() { this.foo = 42; Foo = ‘Fol’; // TypeError: Assignment to constant variable } } const foo = new Foo(); Foo = ‘Fol’; // it’s ok
+ 思路二：
```javascript
class Super {}
class Sub extends Super {}
const sub = new Sub();
Sub.__proto__ === Super;
function Super() {}
function Sub() {}
Sub.prototype = new Super();
Sub.prototype.constructor = Sub;
var sub = new Sub();
Sub.__proto__ === Function.prototype;
- 而通过 ES5 的方式，Sub.proto === Function.prototype
扩展阅读：