在新对象中将原型称为另一个原型

Question

This returns back thisFunction.weather.day() is undefined.. Why? Am i doing this correct?

 'use scrict';

    var thisFunction = function(){this.event(); };

    thisFunction.prototype.weather = function(){

        this.day = "Cloudy";

    };

    thisFunction.prototype.event = function(){

        console.log(thisFunction.weather().day);

    };

    var g = new thisFunction();

Im trying to call the weather function inside of event. As you can see at the bottom theres a new var g that equals new thisFunction(). If I call the weather function inside event thisFunction.prototype.weather().day is undefined. Why?

Answer 1

thisFunction is your constructor function.

It does not have a .weather() method. So, thisFunction.weather is undefined and thisFunction.weather() is an error.

The .weather() method is on the prototype which means its on instances of thisFunction , not on the constructor itself. So, in your code, you could do:

 g.weather()

Or, inside of the .event() method, you could do this:

thisFunction.prototype.event = function(){

    console.log(this.weather());
};

To make this.weather().day work, you'd have to return this from the .weather() method.

thisFunction.prototype.weather = function(){

    this.day = "Cloudy";
    return this;

};

thisFunction.prototype.event = function(){

    console.log(this.weather().day);

};