无法使用对 function 的调用方法创建 object。 如何使用调用方法创建 object？

Question

Here I have created a constructor function. I want to create an object using call method to this function. I have used the empty object as the current object and passed an argument.

 function Circle(radius){ this.radius = radius; this.draw = function(){ console.log('draw'); } } let cirlce1 = Circle.call({}, 1); console.log(cirlce1);

I am getting undefined in the console. I want to know where have I gone wrong?

Answer 1

You have to return the current object in the Circle function. Here you are creating a variable equals to what Circle returns. Because it's not returning anything, you get undefined. So you only have to add a return statement at the end returning this. Which in this case is the empty object you passed originally in call.

function Circle(radius){
    this.radius = radius;
    this.draw = function(){
        console.log('draw');
    }
    return this;
}

let circle = Circle.call({}, 1);
console.log(circle);

After that, your empty object now has the radius property and the draw method. Then you return it. The result is saved in the circle variable.