Ajax vs Traditional Web Applications
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Questions and Answers

What is the primary responsibility of the interface construction in traditional web applications?

  • Manipulation of the Document Object Model (DOM)
  • Background HTTP requests
  • Server processing (correct)
  • Client-side JavaScript manipulations

    • How does user interaction occur in Ajax applications compared to traditional applications?

  • Directly via the server responses
  • Only through page refresh
  • Via form submissions only
  • Through HTTP requests that occur ‘behind the scenes’ (correct)

    • What does the Ajax engine primarily do during a user session?

  • Handles all traditional form submissions
  • Pre-loads data into the browser cache
  • Renders the interface and communicates with the server (correct)
  • Loads all HTML pages directly from the server

    • Which of the following indicates a traditional web application model?

    <p>User waits for the server to process requests</p> Signup and view all the answers

    Which method can be used to identify an Ajax application when inspecting the source?

    <p>Finding XMLHttpRequest or fetch invocations</p> Signup and view all the answers

    What happens to the application during user interactions in an Ajax environment?

    <p>Only data is communicated, keeping the interface responsive</p> Signup and view all the answers

    Which of the following is NOT a feature of Ajax web applications?

    <p>Triggering HTTP requests to load entire web pages</p> Signup and view all the answers

    What is a significant drawback of the classic web application model?

    <p>Users experience delays with every action</p> Signup and view all the answers

    What does the acronym Ajax stand for?

    <p>Asynchronous JavaScript and XML</p> Signup and view all the answers

    Which component is primarily responsible for asynchronous data retrieval in Ajax?

    <p>XMLHttpRequest</p> Signup and view all the answers

    Which technology did Microsoft first implement to enable Ajax in Internet Explorer?

    <p>ActiveX Object</p> Signup and view all the answers

    Which feature is not characteristic of Ajax applications?

    <p>Full-Page Refresh</p> Signup and view all the answers

    What was the main function of the server in an Ajax-enabled application?

    <p>Business Logic Processing</p> Signup and view all the answers

    Which of the following technologies is NOT traditionally associated with Ajax?

    <p>Flash</p> Signup and view all the answers

    Who originated the acronym Ajax?

    <p>Jesse James Garrett</p> Signup and view all the answers

    Which standard encompasses similar functionality to the XMLHttpRequest object?

    <p>W3C DOM Level 3 Load and Save Specification</p> Signup and view all the answers

    What is one primary benefit of using Ajax in web applications?

    <p>It cuts down on user wait time.</p> Signup and view all the answers

    Which operation can the Ajax engine handle on its own without server interaction?

    <p>Editing data in memory.</p> Signup and view all the answers

    What is a key feature of the Ajax model compared to traditional web application models?

    <p>Operates asynchronously.</p> Signup and view all the answers

    What does the Ajax engine implement to initiate user actions?

    <p>JavaScript calls.</p> Signup and view all the answers

    How does the Ajax engine improve application responsiveness for users?

    <p>By allowing background data retrieval without halting user interaction.</p> Signup and view all the answers

    What needs to be created to handle asynchronous requests in Ajax?

    <p>An instance of the XMLHttpRequest object.</p> Signup and view all the answers

    What is a disadvantage of traditional web application models compared to Ajax?

    <p>Users see frequent hourglass cursors.</p> Signup and view all the answers

    What form of data can the Ajax engine retrieve from the server?

    <p>JSON or XML data.</p> Signup and view all the answers

    What are the two required parameters for the open() method?

    <p>HTTP method and URL</p> Signup and view all the answers

    What is the primary purpose of the send() method in the XMLHttpRequest object?

    <p>To initiate the transaction</p> Signup and view all the answers

    Which readyState value indicates that the transaction is complete?

    <p>4</p> Signup and view all the answers

    In what scenario should the POST method be used with the XMLHttpRequest object?

    <p>When sending large amounts of data to the server</p> Signup and view all the answers

    What type of data does the responseText property return?

    <p>A string representation of data</p> Signup and view all the answers

    Which method should typically be designed around the onreadystatechange event?

    <p>send()</p> Signup and view all the answers

    What is a key characteristic of the responseXML property of the XMLHttpRequest object?

    <p>It is a full XML document node object</p> Signup and view all the answers

    Why is it considered safer to send requests asynchronously in XMLHttpRequest?

    <p>It allows multiple requests to be processed concurrently</p> Signup and view all the answers

    What are the possible values for the responseType attribute of the XMLHttpRequest object?

    <p>arraybuffer, blob, document, json, text</p> Signup and view all the answers

    In the onreadystatechange function, under what condition is the response processed?

    <p>When req.readyState is 4 and req.status is 200</p> Signup and view all the answers

    Which method is used to alert the user about a problem with the XMLHttpRequest?

    <p>alert()</p> Signup and view all the answers

    What must the protocol be for the page accessing the XMLHttpRequest object?

    <p>http:</p> Signup and view all the answers

    What security policy does the XMLHttpRequest comply with while running in a browser?

    <p>Same-origin policy</p> Signup and view all the answers

    What happens if a script tries to access a resource from a different domain using XMLHttpRequest?

    <p>The request will fail due to security restrictions.</p> Signup and view all the answers

    What does req.responseText return when the responseType is set to json?

    <p>A parsed JSON object</p> Signup and view all the answers

    Which browsers are specifically mentioned as having potential issues with testing XMLHttpRequest from a local hard disk?

    <p>Mozilla and Internet Explorer</p> Signup and view all the answers

    What type of data can be accessed from any domain without security risk?

    <p>Images</p> Signup and view all the answers

    What is one of the ways mentioned to circumvent cross-domain security restrictions?

    <p>Setting up a web proxy</p> Signup and view all the answers

    What must a server be configured to accept if using CORS?

    <p>CORS requests</p> Signup and view all the answers

    Why is it not possible for a web application to directly access data from a different domain?

    <p>It violates the browser's cross-domain security policy.</p> Signup and view all the answers

    Which of the following accurately describes the Fetch API?

    <p>A JavaScript interface for accessing and manipulating requests and responses.</p> Signup and view all the answers

    What is one drawback of using a proxy for cross-domain requests?

    <p>It requires additional server-side configuration.</p> Signup and view all the answers

    Which function does the Fetch API provide for making network requests?

    <p>fetch()</p> Signup and view all the answers

    What is the purpose of CORS in web applications?

    <p>To allow secure cross-origin requests.</p> Signup and view all the answers

    Study Notes

    Ajax - Asynchronous JavaScript + XML

    • Ajax is not a single technology but rather a combination of several technologies
    • It incorporates standards-based presentation using XHTML, CSS, and dynamic display/interaction via the Document Object Model (DOM)
    • Data interchange can use XML, but JSON is more common today
    • Asynchronous data retrieval uses XMLHttpRequest
    • JavaScript binds all these elements together
    • Server-side logic is focused on business logic, not display logic

    Ajax Application Characteristics

    • Ajax applications are interactive, rather than just static web pages
    • User interaction is continuous and smooth
    • Data is loaded asynchronously without requiring page refresh
    • Animations and dynamic icons enhance user engagement
    • New widgets, such as dropdown menus, tabs, and lists are added
    • New styles of interaction, like drag-and-drop and keyboard shortcuts are used

    Comparing Traditional vs. AJAX Websites

    Feature Traditional AJAX
    Interface Constructed primarily by the server Manipulated by client-side JavaScript
    User Interaction Form submissions HTTP requests (behind the scenes)
    Page Refresh An entire page is loaded per interaction Updates are made without full page refresh
    Application State Application unavailable while processing Responsive during processing

    How to Recognize an Ajax Application Internally

    • Examine the Javascript source code for XMLHttpRequest or fetch calls
    • Look for JavaScript loading other JavaScript files
    • Look for code passed as text strings to the server
    • Examine Javascript code between //
    • Search for Javascript code creating IFRAMEs or including jQuery Ajax functions.

    The Classic vs. Ajax Web Application Model

    • Classic Model: User actions trigger HTTP requests to the server, which then sends back an HTML page. User waits for each step.
    • Ajax Model: An intermediary (Ajax engine) handles requests and updates, allowing interactions to happen asynchronously. No waiting for full page reloads.

    AJAX: Client-Side Processing

    • AJAX significantly reduces the time the user has to wait for server actions.
    • Reduces the amount of network traffic that the application sends to the web server and then back to the browser.
    • Client-side processing enhances interactivity and responsiveness of applications.

    Security Issues with AJAX

    • AJAX inherits security policies of typical JavaScript
    • For cross-domain interactions, the URL must be from the same domain as the page that contains the script.
    • Using a proxy or CORS configurations often help mitigate cross-domain issues.

    Cross-Origin Resource Sharing (CORS)

    • CORS is a mechanism that enables a web application to make requests to other domains.
    • The server explicitly permits such requests through HTTP headers (like Access-Control-Allow-Origin)
    • Browsers use this information to decide whether to allow access.

    Alternative: Fetch API

    • Fetch API is a more modern way to fetch resources asynchronously with improved error handling and global methods.
    • Promises returned from fetch won't reject on HTTP errors, even if the returned status code is not 200.
    • It doesn't automatically receive cookies from other domains unless credentials are set.
    • Main characteristics differ from jQuery. AJAX in three ways: Promises, HTTP errors, cross-domain cookies

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    Description

    This quiz explores the differences and functionalities between traditional web applications and Ajax applications. It covers user interactions, responsibilities of interface construction, and features specific to each model. Test your knowledge on this modern web development topic!

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