Introduction to AJAX: What is AJAX and How it Works
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Questions and Answers

What does the acronym AJAX stand for?

  • Asynchronous JavaScript and XML (correct)
  • Accelerated JavaScript Application eXecution
  • Advanced JavaScript and XML Access
  • Advanced JavaScript Application eXtension

    • What is the primary purpose of the XMLHttpRequest object in AJAX?

  • To request data from a web server (correct)
  • To update web pages synchronously
  • To display data on a web page
  • To create a new programming language

    • Who introduced AJAX to the world in 2005?

  • Tim Berners-Lee
  • Bill Gates
  • Jesse James Garrett (correct)
  • Steve Jobs

    • What is a common misconception about AJAX?

    <p>It only uses XML to transport data</p> Signup and view all the answers

    What is the purpose of AJAX in web development?

    <p>To allow web pages to be updated asynchronously</p> Signup and view all the answers

    When was the first draft of the XMLHttpRequest object specification released by the W3C?

    <p>5th April 2006</p> Signup and view all the answers

    Which of the following is the purpose of the onreadystatechange property?

    <p>To define a function to be executed when the readyState changes.</p> Signup and view all the answers

    What is the status code for 'Page not found'?

    <p>404</p> Signup and view all the answers

    What is the purpose of the xhttp.open() method?

    <p>To specify the request type and URL.</p> Signup and view all the answers

    What is the value of the readyState property when the request is finished and the response is ready?

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

    What is the purpose of the xhttp.send() method?

    <p>To send the request to the server.</p> Signup and view all the answers

    What is the purpose of the abort() method in an XMLHttpRequest object?

    <p>To cancel the current request</p> Signup and view all the answers

    Which property of the XMLHttpRequest object holds the status of the request?

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

    What is the purpose of the open() method in an XMLHttpRequest object?

    <p>To specify the request method and URL</p> Signup and view all the answers

    What is the purpose of the setRequestHeader() method in an XMLHttpRequest object?

    <p>To add a label/value pair to the header</p> Signup and view all the answers

    What is the purpose of the send() method in an XMLHttpRequest object when used with a string parameter?

    <p>To send the request to the server for a POST request</p> Signup and view all the answers

    What is the value of the status property in an XMLHttpRequest object when the request is successful?

    <p>200</p> Signup and view all the answers

    Study Notes

    XMLHttpRequest Object

    • Syntax for creating an XMLHttpRequest object: variable = new XMLHttpRequest()

    XMLHttpRequest Object Methods

    • abort(): Cancels the current request
    • getAllResponseHeaders(): Returns header information
    • getResponseHeader(): Returns specific header information
    • open(method, url, async, user, psw): Specifies the request
      • method: the request type (GET or POST)
      • url: the file location
      • async: true (asynchronous) or false (synchronous)
      • user: optional user name
      • psw: optional password
    • send(): Sends the request to the server (used for GET requests)
    • send(string): Sends the request to the server (used for POST requests)
    • setRequestHeader(): Adds a label/value pair to the header to be sent

    XMLHttpRequest Object Properties

    • onreadystatechange: Defines a function to be called when the readyState property changes
    • readyState: Holds the status of the XMLHttpRequest
      • 0: request not initialized
      • 1: server connection established
      • 2: request received
      • 3: processing request
      • 4: request finished and response is ready
    • responseText: Returns the response data as a string
    • responseXML: Returns the response data as XML data
    • status: Returns the status-number of a request
      • 200: "OK"
      • 403: "Forbidden"
      • 404: "Not Found"
    • statusText: Returns the status-text (e.g. "OK" or "Not Found")

    Introduction to AJAX

    • AJAX stands for Asynchronous JavaScript and XML
    • AJAX is not a programming language, but a combination of:
      • Browser built-in XMLHttpRequest object
      • JavaScript and HTML DOM
    • AJAX allows web pages to be updated asynchronously by exchanging data with a web server behind the scenes

    History of AJAX

    • Jesse James Garrett introduced AJAX to the world on 18th February 2005
    • W3C released the first draft of XMLHttpRequest object specifications on 5th April 2006

    How AJAX Works

    • Uses the XMLHttpRequest object to exchange data with a server behind the scenes
    • Steps to send a request to a server:
      • Use the open() and send() methods of the XMLHttpRequest object
      • Example: xhttp.open("GET", "ajax_info.txt", true); xhttp.send();

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    Description

    Test your knowledge of AJAX, a technology that allows for asynchronous web page updates. Learn about the XMLHttpRequest object, how AJAX works, and what AJAX stands for. Discover the basics of AJAX and its applications.

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