es6 class class

1, ES6 provided closer to the traditional language of the writing, we introduce Class (Class) concept as an object template. By classkeyword, you can define classes.

2、

//定义类
class Point {
  constructor(x, y) {
    this.x = x;
    this.y = y;
  }

  toString() {
    return '(' + this.x + ', ' + this.y + ')';
  }
}

The above code defines a "class", there can be seen a constructormethod, which is the constructor, the thiskeyword represents the object instance. That is, the constructor of ES5 Point, ES6 corresponding to the Pointclass constructor.

3, define methods "class" of the time, does not require preceded by functionthe keyword directly into the function definition went on it. Further, the method does not require between commas, plus error.

4, the constructor prototypeproperty, continues to exist above the "class" of for ES6. In fact, all methods defined in the class are the class prototypeattributes above.

class Point {
  constructor(){
    // ...
  }

  toString(){
    // ...
  }

  toValue(){
    // ...
  }
}

// 等同于

Point.prototype = {
  toString(){},
  toValue(){}
};

5, Object.assignthe method can easily add more methods to the class.

class Point {
  constructor(){
    // ...
  }
}

Object.assign(Point.prototype, {
  toString(){},
  toValue(){}
});

6, the interior of all defined class methods are not enumerable (non-enumerable). This behavior is inconsistent with ES5.

7, the attribute name of the class, you can use an expression.

let methodName = "getArea";
class Square{
  constructor(length) {
    // ...
  }

  [methodName]() {
    // ...
  }
}

In the above code, Squarethe method name of the class getArea, is obtained from the expression.

8, constructoris the default class method, by newgenerating a command object instance, the method is automatically invoked. There must be a class constructormethod, if no explicit definition, an empty constructormethod will be added by default. constructorThe method returns an instance of a default object (i.e. this), you can specify another object returned.

9, the class constructor is not used newis not invoked, being given.

10, by way of example may be a __proto__method of adding to the Class property.

var p1 = new Point(2,3);
var p2 = new Point(3,2);

p1.__proto__.printName = function () { return 'Oops' };

p1.printName() // "Oops"
p2.printName() // "Oops"

var p3 = new Point(4,2);
p3.printName() // "Oops"

11, using examples of __proto__properties overwrite prototype must be very careful not recommended, because it will change the original definition of the Class, affecting all instances.

12, Class variable lift (hoist) does not exist.

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