新增类和继承的概念

类定义　　更直观，OOP风格和样板免费类。

//ES6
class Shape {
    constructor (id, x, y) {
        this.id = id
        this.move(x, y)
    }
    move (x, y) {
        this.x = x
        this.y = y
    }
}

//ES5
var Shape = function (id, x, y) {
    this.id = id;
    this.move(x, y);
};
Shape.prototype.move = function (x, y) {
    this.x = x;
    this.y = y;
};

友情链接link:http://es6-features.org/#ClassDefinition

类继承

//ES6
class Rectangle extends Shape {
    constructor (id, x, y, width, height) {
        super(id, x, y)
        this.width  = width
        this.height = height
    }
}
class Circle extends Shape {
    constructor (id, x, y, radius) {
        super(id, x, y)
        this.radius = radius
    }
}

//ES5
var Rectangle = function (id, x, y, width, height) {
    Shape.call(this, id, x, y);
    this.width  = width;
    this.height = height;
};
Rectangle.prototype = Object.create(Shape.prototype);
Rectangle.prototype.constructor = Rectangle;
var Circle = function (id, x, y, radius) {
    Shape.call(this, id, x, y);
    this.radius = radius;
};
Circle.prototype = Object.create(Shape.prototype);
Circle.prototype.constructor = Circle;

　link:http://es6-features.org/#ClassInheritance

类继承，由表达式继承

//ES6

var aggregation = (baseClass, ...mixins) => {
    let base = class _Combined extends baseClass {
        constructor (...args) {
            super(...args)
            mixins.forEach((mixin) => {
                mixin.prototype.initializer.call(this)
            })
        }
    }
    let copyProps = (target, source) => {
        Object.getOwnPropertyNames(source)
            .concat(Object.getOwnPropertySymbols(source))
            .forEach((prop) => {
            if (prop.match(/^(?:constructor|prototype|arguments|caller|name|bind|call|apply|toString|length)$/))
                return
            Object.defineProperty(target, prop, Object.getOwnPropertyDescriptor(source, prop))
        })
    }
    mixins.forEach((mixin) => {
        copyProps(base.prototype, mixin.prototype)
        copyProps(base, mixin)
    })
    return base
}

class Colored {
    initializer ()     { this._color = "white" }
    get color ()       { return this._color }
    set color (v)      { this._color = v }
}

class ZCoord {
    initializer ()     { this._z = 0 }
    get z ()           { return this._z }
    set z (v)          { this._z = v }
}

class Shape {
    constructor (x, y) { this._x = x; this._y = y }
    get x ()           { return this._x }
    set x (v)          { this._x = v }
    get y ()           { return this._y }
    set y (v)          { this._y = v }
}

class Rectangle extends aggregation(Shape, Colored, ZCoord) {}

var rect = new Rectangle(7, 42)
rect.z     = 1000
rect.color = "red"
console.log(rect.x, rect.y, rect.z, rect.color)


//ES5

var aggregation = function (baseClass, mixins) {
    var base = function () {
        baseClass.apply(this, arguments);
        mixins.forEach(function (mixin) {
            mixin.prototype.initializer.call(this);
        }.bind(this));
    };
    base.prototype = Object.create(baseClass.prototype);
    base.prototype.constructor = base;
    var copyProps = function (target, source) {
        Object.getOwnPropertyNames(source).forEach(function (prop) {
            if (prop.match(/^(?:constructor|prototype|arguments|caller|name|bind|call|apply|toString|length)$/))
                return
            Object.defineProperty(target, prop, Object.getOwnPropertyDescriptor(source, prop))
        })
    }
    mixins.forEach(function (mixin) {
        copyProps(base.prototype, mixin.prototype);
        copyProps(base, mixin);
    });
    return base;
};

var Colored = function () {};
Colored.prototype = {
    initializer: function ()  { this._color = "white"; },
    getColor:    function ()  { return this._color; },
    setColor:    function (v) { this._color = v; }
};

var ZCoord = function () {};
ZCoord.prototype = {
    initializer: function ()  { this._z = 0; },
    getZ:        function ()  { return this._z; },
    setZ:        function (v) { this._z = v; }
};

var Shape = function (x, y) {
    this._x = x; this._y = y;
};
Shape.prototype = {
    getX: function ()  { return this._x; },
    setX: function (v) { this._x = v; },
    getY: function ()  { return this._y; },
    setY: function (v) { this._y = v; }
}

var _Combined = aggregation(Shape, [ Colored, ZCoord ]);
var Rectangle = function (x, y) {
    _Combined.call(this, x, y);
};
Rectangle.prototype = Object.create(_Combined.prototype);
Rectangle.prototype.constructor = Rectangle;

var rect = new Rectangle(7, 42);
rect.setZ(1000);
rect.setColor("red");
console.log(rect.getX(), rect.getY(), rect.getZ(), rect.getColor());

基类访问对基类构造函数和方法的直观访问。

//ES6

class Shape {
    …
    toString () {
        return `Shape(${this.id})`
    }
}
class Rectangle extends Shape {
    constructor (id, x, y, width, height) {
        super(id, x, y)
        …
    }
    toString () {
        return "Rectangle > " + super.toString()
    }
}
class Circle extends Shape {
    constructor (id, x, y, radius) {
        super(id, x, y)
        …
    }
    toString () {
        return "Circle > " + super.toString()
    }
}




//ES5
var Shape = function (id, x, y) {
    …
};
Shape.prototype.toString = function (x, y) {
    return "Shape(" + this.id + ")"
};
var Rectangle = function (id, x, y, width, height) {
    Shape.call(this, id, x, y);
    …
};
Rectangle.prototype.toString = function () {
    return "Rectangle > " + Shape.prototype.toString.call(this);
};
var Circle = function (id, x, y, radius) {
    Shape.call(this, id, x, y);
    …
};
Circle.prototype.toString = function () {
    return "Circle > " + Shape.prototype.toString.call(this);
};

静态成员静态类成员的简单支持

//ES6

class Rectangle extends Shape {
    …
    static defaultRectangle () {
        return new Rectangle("default", 0, 0, 100, 100)
    }
}
class Circle extends Shape {
    …
    static defaultCircle () {
        return new Circle("default", 0, 0, 100)
    }
}
var defRectangle = Rectangle.defaultRectangle()
var defCircle    = Circle.defaultCircle()




//ES5

var Rectangle = function (id, x, y, width, height) {
    …
};
Rectangle.defaultRectangle = function () {
    return new Rectangle("default", 0, 0, 100, 100);
};
var Circle = function (id, x, y, width, height) {
    …
};
Circle.defaultCircle = function () {
    return new Circle("default", 0, 0, 100);
};
var defRectangle = Rectangle.defaultRectangle();
var defCircle    = Circle.defaultCircle();

Getter/Setter

//ES6

class Rectangle {
    constructor (width, height) {
        this._width  = width
        this._height = height
    }
    set width  (width)  { this._width = width               }
    get width  ()       { return this._width                }
    set height (height) { this._height = height             }
    get height ()       { return this._height               }
    get area   ()       { return this._width * this._height }
}
var r = new Rectangle(50, 20)
r.area === 1000



//ES5

var Rectangle = function (width, height) {
    this._width  = width;
    this._height = height;
};
Rectangle.prototype = {
    set width  (width)  { this._width = width;               },
    get width  ()       { return this._width;                },
    set height (height) { this._height = height;             },
    get height ()       { return this._height;               },
    get area   ()       { return this._width * this._height; }
};
var r = new Rectangle(50, 20);
r.area === 1000;

http://es6-features.org/#GetterSetter

新增类和继承的概念

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