Object-oriented programming (OOP) implementation with asynchronous JavaScript and XML (

Question

Object-oriented programming (OOP) implementation with asynchronous JavaScript and XML (

... I'm currently facing a situation where I have an object:

function Page(daoService) {
    this.daoService = daoService;
    this.gamesList = this.daoService.getGamesList();
}

// Rendering thumbs for main page
Page.prototype.renderThumbs = function(idContainer){
    var container = document.getElementById(idContainer);
    for (var i = 0; i < this.gamesList.length; i++) {
        var thumbNode = document.createTextNode("<div class='thumbIcon'></div>");
        thumbNode.style.backgroundImage = Const.PATH_THUMBS + this.gamesList.gameTitleseo;
        container.appendChild(thumbNode);
    }
};

In addition, there is a function in my code that utilizes the aforementioned object:

document.onreadystatechange = function() { 
    if (document.readyState == "interactive") { 
        // Initialization of elements
        // Setting global dao service
        var daoService = AjaxService();

        // Initialization for page object
        var page = new Page(daoService);
        page.renderThumbs("homePageContainer");
    } 
}

The problem I am encountering is that when I call page.renderThumbs, the field this.gamesList has not yet been initialized as it is waiting for an ajax response from the server. Can someone provide guidance on how to address this issue and suggest any necessary changes to my approach? Thank you.

javascript ajax oop document-ready

Answer 1

Answer №1

To effectively handle an asynchronous method, it is necessary to configure the getGamesList on daoService. Here is a basic outline of what needs to be done:

DaoService.prototype.getGamesList = function(callback) {

    var self = this;

    // Check if gamesList has already been populated by a previous call
    if (this.gamesList) {
        // If values exist in gamesList property, execute the callback.
        callback(this.gamesList);
    }
    else {
        // If gamesList is empty, initiate the ajax call.
        $.ajax('URL').done(function(data) {
            // Process the data received from the server.
            self.gamesList = data;
            callback(this.gamesList);
        });
    }


}

You can then utilize the getGamesList method within renderThumbs in the following manner:

Page.prototype.renderThumbs = function(idContainer){
    var container = document.getElementById(idContainer);

    // The anonymous function will be invoked regardless of whether the list was
    // already populated in daoService or an ajax call is triggered.
    this.daoService.getGamesList(function(gamesList) {
        for (var i = 0; i < gamesList.length; i++) {
            var thumbNode = document.createTextNode("<div class='thumbIcon'></div>");
            thumbNode.style.backgroundImage = Const.PATH_THUMBS + gamesList[i].gameTitleseo;
            container.appendChild(thumbNode);
        }
    });
};

Answer 2

To effectively handle an asynchronous method, it is necessary to configure the getGamesList on daoService. Here is a basic outline of what needs to be done:

DaoService.prototype.getGamesList = function(callback) {

    var self = this;

    // Check if gamesList has already been populated by a previous call
    if (this.gamesList) {
        // If values exist in gamesList property, execute the callback.
        callback(this.gamesList);
    }
    else {
        // If gamesList is empty, initiate the ajax call.
        $.ajax('URL').done(function(data) {
            // Process the data received from the server.
            self.gamesList = data;
            callback(this.gamesList);
        });
    }


}

You can then utilize the getGamesList method within renderThumbs in the following manner:

Page.prototype.renderThumbs = function(idContainer){
    var container = document.getElementById(idContainer);

    // The anonymous function will be invoked regardless of whether the list was
    // already populated in daoService or an ajax call is triggered.
    this.daoService.getGamesList(function(gamesList) {
        for (var i = 0; i < gamesList.length; i++) {
            var thumbNode = document.createTextNode("<div class='thumbIcon'></div>");
            thumbNode.style.backgroundImage = Const.PATH_THUMBS + gamesList[i].gameTitleseo;
            container.appendChild(thumbNode);
        }
    });
};

Answer 3

Answer №2

Implement promises within your daoService to handle asynchronous results effectively. jQuery offers a reliable promise framework for this purpose. Symbolic representation:

function DaoService() {
   this.getGamesList = function() {
       return $.Deferred(function(defer) {
            //Perform an ajax request here and wait for the callback/complete
            //Replace DoAjax with your own ajax function or preferably use jQuery ajax, which supports promises
            DoAjax(function onReady(result) {
                defer.resolve(result.data);    
            });

       }).promise();
   }
}

In your page class, whenever you require the games list, utilize the following method. It ensures that data is only downloaded once, subsequently using the already retrieved information.

Page.prototype.renderThumbs = function(idContainer){
    var container = document.getElementById(idContainer);
    this.daoService.getGamesList().then(function(gamesList) {
       for (var i = 0; i < gamesList.length; i++) {
          var gameListItem = gamesList[i];
          //Perform necessary HTML concatenations or consider using templating options
       });
    });
    }
};

Answer 4

Implement promises within your daoService to handle asynchronous results effectively. jQuery offers a reliable promise framework for this purpose. Symbolic representation:

function DaoService() {
   this.getGamesList = function() {
       return $.Deferred(function(defer) {
            //Perform an ajax request here and wait for the callback/complete
            //Replace DoAjax with your own ajax function or preferably use jQuery ajax, which supports promises
            DoAjax(function onReady(result) {
                defer.resolve(result.data);    
            });

       }).promise();
   }
}

In your page class, whenever you require the games list, utilize the following method. It ensures that data is only downloaded once, subsequently using the already retrieved information.

Page.prototype.renderThumbs = function(idContainer){
    var container = document.getElementById(idContainer);
    this.daoService.getGamesList().then(function(gamesList) {
       for (var i = 0; i < gamesList.length; i++) {
          var gameListItem = gamesList[i];
          //Perform necessary HTML concatenations or consider using templating options
       });
    });
    }
};

Object-oriented programming (OOP) implementation with asynchronous JavaScript and XML (

Answer №1

Answer №2

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