js实现工厂模式

class Circle{
	constructor(){
		this.shape="circle"
	}
}
class Rectangle{
	constructor(){
		this.shape="rectangle"
	}
}
class ShapeFactory{
	constructor(){
	}
	getShapeInstance(shapeType){
		shapeType=shapeType[0].toUpperCase()+shapeType.substr(1).toLowerCase()
		return eval(`new ${shapeType}()`)
	}
}
let shapeFactory=new ShapeFactory()
console.log(shapeFactory.getShapeInstance('circle'))
console.log(shapeFactory.getShapeInstance('rectangle'))