Javascript - can类路径有名称空间

Javascript - can class paths have namespaces?

本文关键字：有名称 空间 路径 can Javascript      更新时间：2023-09-26

我知道我可以用下面的代码创建一个类:

class Polygon {
    constructor(height, width) {
      this.height = height;
      this.width = width;
    }
}

然而，我希望这个Polygon类驻留在一个名为Model的命名空间中，这样我就可以像这样实例化Polygon对象:

var myNewPolygon = new Model.Polygon(10, 50);

这可能吗?

我已经试过了:

var Model = Model || {};
class Model.Polygon {
    constructor() {
      this.height = height;
      this.width = width;
    }
}
var myNewPolygon = new Model.Polygon(10, 50);

但是这会导致第2行出现Uncaught SyntaxError: Unexpected token .。

我也试过了:

var Model = Model || {};
class Polygon {
    constructor(height, width) {
      this.height = height || 0;
      this.width = width || 0;
    }
}
Model.Polygon = new Polygon();
var myNewPolygon = new Model.Polygon(10, 50);

但是这会导致第9行出现Uncaught TypeError: Model.Polygon is not a constructor

快到了。

var Model = Model || {};
Model.Polygon = class {
    constructor(height, width) {
      this.height = height || 0;
      this.width = width || 0;
    }
}
var myNewPolygon = new Model.Polygon(10, 50);

类可以像函数一样被命名(又名"匿名")，也可以像函数一样，未命名的类可以被赋值给变量，就像上面的Model.Polygon = class { ... }

如果需要类在类体中引用自己，那么可以给它起一个名字。请注意，类名在类体之外是不可用的。

var Model = Model || {};
Model.Polygon = class Polygon {
    constructor(height, width) {
      this.height = height || 0;
      this.width = width || 0;
    }
    equals(other){
      // Returns true if other is also an instance of Polygon
      // and height and width are the same.
      return ( other instanceof Polygon )     &&
             ( other.height === this.height ) &&
             ( other.width === this.width );
    }
}
var myNewPolygon1 = new Model.Polygon(10, 50);
var myNewPolygon2 = new Model.Polygon(10, 50);
myNewPolygon1.equals( myNewPolygon2 ); // returns true
myNewPolygon1.equals({ height: 10, width: 50 }); // returns false
var myNewPolygon3 = new Polygon(10, 50); // Uncaught ReferenceError: Polygon is not defined
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