What could be the reason for the failure of calling a function within an object using "this.myFunction"?

Question

What could be the reason for the failure of calling a function within an object using "this.myFunction"?

Reviewing these two code snippets, I am faced with a puzzle. The first code block fails to execute, while the second one successfully runs. This has left me perplexed, and I am seeking clarification from those who can shed some light on the matter.

[My current project involves developing a straightforward game using jQuery for compatibility with webkit browsers (and eventually for packaging with Titanium).]

Upon analyzing the first example, Firebug alerts me that "this.checkCloud" is not recognized as a function.

function Cloud(){

    this.checkCloud = function(){
      alert('test');            
    }

    $("#"+this.cloudName).click(function(){
        this.checkCloud();
    });

}

Interestingly, the following implementation proves to be successful:

function Cloud(){

    this.checkCloud = function(){
      alert('test');            
    }

    var _this = this;

    $("#"+this.cloudName).click(function(){
        _this.checkCloud();
    });

}

The second version functions flawlessly.

What is the reason behind the failure of the first code? Could it be due to "this.checkCloud" being located within the anonymous function?

javascript oop this

Answer 1

Answer №1

in this particular instance:

$("#"+this.cloudName).click(function(){
        this.validateCloud();
    });

this points to the chosen element (a jquery object).

One effective approach is to utilize private functions

var validateCloud = function(){
      alert('testing');            
    }

this method allows for easy invocation within the anonymous function

$("#"+this.cloudName).click(function(){
            validateCloud();
        });

Answer 2

in this particular instance:

$("#"+this.cloudName).click(function(){
        this.validateCloud();
    });

this points to the chosen element (a jquery object).

One effective approach is to utilize private functions

var validateCloud = function(){
      alert('testing');            
    }

this method allows for easy invocation within the anonymous function

$("#"+this.cloudName).click(function(){
            validateCloud();
        });

Answer 3

Answer №2

The reason behind this phenomenon lies in the fact that the interpretation of this can vary every time a new scope is created through a function. The interpretation of this is determined by the method of invocation of the function (which can be incredibly complex). To overcome this, a simple solution is to create an additional variable that stores this in the scope where this holds the desired values, and then utilize this variable instead of this to reference the same object in future function scopes where this may differ.

Answer 4

The reason behind this phenomenon lies in the fact that the interpretation of this can vary every time a new scope is created through a function. The interpretation of this is determined by the method of invocation of the function (which can be incredibly complex). To overcome this, a simple solution is to create an additional variable that stores this in the scope where this holds the desired values, and then utilize this variable instead of this to reference the same object in future function scopes where this may differ.

Answer 5

Answer №3

Give this a shot:

function Sky(){

    this.verifySky = function(){
      alert('exam');            
    }

    var verification = this.verifySky;

    $("#" + this.skyName).click(function(){
         verification();
     });
}

Answer 6

Give this a shot:

function Sky(){

    this.verifySky = function(){
      alert('exam');            
    }

    var verification = this.verifySky;

    $("#" + this.skyName).click(function(){
         verification();
     });
}

Answer 7

Answer №4

By attaching an event listener to an element in jQuery, the reference of this is set to the element itself. However, when you define the _this variable, you are establishing a closure that jQuery is unable to manipulate, even if it tried.

Answer 8

By attaching an event listener to an element in jQuery, the reference of this is set to the element itself. However, when you define the _this variable, you are establishing a closure that jQuery is unable to manipulate, even if it tried.

What could be the reason for the failure of calling a function within an object using "this.myFunction"?

Answer №1

Answer №2

Answer №3

Answer №4

Similar questions

What is the reason for using a string as the index of an array in the following code?

What causes the malfunction of the save function in express?

Most effective method to retrieve yesterday's data

The function ajax does not recognize response.forEach as a valid function

What is the best way to combine the existing array data with the previous array data in JavaScript?

What's preventing me from using the left click function on my published blog post?

Using the MongoDB aggregate framework to determine the total employee count per unique state

The functionality of sending form data via Express.js router is restricted

Incorporate a dynamic fading effect for text and images using JQuery

Is it necessary to have NodeJs in order to host a React app on a server?

Utilize prop-types inheritance when a component is rendered via props

Pass a parameter to an AJAX request in order to retrieve data from a JSON file that is limited to a specific

Utilizing Javascript for a Stopwatch/Countdown in the Format: 00:00:00

Creating a JavaScript interface for an XML API generated by Rails?

How can I include a JSON object in an angularjs $scope variable?

How can I track the number of correct answers in a ReactJS quiz with an auto-submit feature and a timer that stops?

Unexpected state being returned by Vuex

Is there a way to track dynamic changes in window dimensions within Vue?

Modifying the URL path while navigating through pages with ajax and jQuery

react-leaflet LayerSelection creates redundant entries in table