JSON and JavaScript Basics

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary purpose of a JSON file?

  • To convert JSON data into classes and attributes of a programming language
  • To send data from the server to the browser
  • To load data from the server or send data to it (correct)
  • To assign a variable to a JavaScript object

What is the role of parsers in JSON processing on the server side?

  • To load JSON data from the server to the browser
  • To convert JSON data into JavaScript objects
  • To process the JSON file and may even convert it into classes and attributes of the language (correct)
  • To send JSON data from the browser to the server

How can a JSON file be loaded from the server in JavaScript?

  • By including the file into the HTML page as a JavaScript.json external file
  • By converting the JSON file into a JavaScript object
  • By using the eval() function
  • By using the XMLHttpRequest() function or directly including the file into the HTML page (correct)

Who is the original developer of JSON?

<p>Douglas Crockford (C)</p> Signup and view all the answers

What is the purpose of the JavaScript eval() function in relation to JSON?

<p>To convert JSON data into a JavaScript object (A)</p> Signup and view all the answers

What is the ECMA standard based on?

<p>Netscape’s JavaScript and Microsoft’s Jscript (B)</p> Signup and view all the answers

What is the primary purpose of the same origin policy in browsers?

<p>To prevent malicious scripts from accessing sensitive information (D)</p> Signup and view all the answers

What determines whether a document or script is considered to be from the same origin?

<p>The protocol and host of the URL (C)</p> Signup and view all the answers

What is the outcome of a script accessing a document from http://www.example.com:81/dir2/other.json when the current page is http://www.example.com/dir/page.html?

<p>Failure, because the port number is different (B)</p> Signup and view all the answers

How can JSON be used to bypass the same origin policy?

<p>By setting the src attribute of a script tag to a URL from another server (B)</p> Signup and view all the answers

What is the advantage of using JSON to bypass the same origin policy?

<p>It enables cross-domain data retrieval (B)</p> Signup and view all the answers

In what year was the tag available in HTML, enabling the use of JSON to bypass the same origin policy?

<p>1994 (A)</p> Signup and view all the answers

What is the primary function of the XMLHttpRequest object?

<p>To send HTTP requests to a server (A)</p> Signup and view all the answers

What is the purpose of the req.readyState property in the XMLHttpRequest code?

<p>To check the status of the HTTP request (D)</p> Signup and view all the answers

What does the eval() function do in the JavaScript callback?

<p>Parses JSON data and creates an object (C)</p> Signup and view all the answers

How is the value of the 'title' field accessed in the JavaScript code?

<p>doc.commands.title (A)</p> Signup and view all the answers

What is the purpose of the req.send(null) method call?

<p>To send the HTTP request to the server (B)</p> Signup and view all the answers

What is the role of the Global Object in the context of the eval() function?

<p>It is a function property that evaluates a string as JavaScript code (D)</p> Signup and view all the answers

What is the purpose of the 'jsonp' dataType in jQuery.ajax()?

<p>To load a JSON block using JSONP and add a callback parameter to the URL (C)</p> Signup and view all the answers

What is the default callback function name used in a JSONP request?

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

What happens to the JSON response when the 'json' dataType is specified?

<p>It is parsed using jQuery.parseJSON before being passed to the success handler (C)</p> Signup and view all the answers

What is the purpose of the 'dataType' option in jQuery.ajax()?

<p>To specify the type of data expected from the server (A)</p> Signup and view all the answers

What is the effect of specifying the 'jsonp' option in a jQuery.ajax() request?

<p>It adds an extra '?callback=?' to the end of the URL (D)</p> Signup and view all the answers

What is the result of parsing a JSON response when the 'json' dataType is specified?

<p>A JavaScript object is returned (B)</p> Signup and view all the answers

What is the main limitation of data retrieval that the JSON and Dynamic Script Tag 'Hack' aims to overcome?

<p>Data can only be retrieved from a single domain. (D)</p> Signup and view all the answers

What is the purpose of the 'noCacheIE' variable in the JSONScriptRequest class?

<p>To prevent caching of requests in Internet Explorer. (A)</p> Signup and view all the answers

What is the function of the 'buildScriptTag' method in the JSONScriptRequest class?

<p>To create the script tag and set its attributes. (C)</p> Signup and view all the answers

What is the purpose of the 'scriptCounter' variable in the JSONScriptRequest class?

<p>To keep track of the number of script tags created. (D)</p> Signup and view all the answers

What is the main functionality of the JSONScriptRequest class?

<p>To create a dynamic script tag and set its src attribute. (C)</p> Signup and view all the answers

What is the significance of the line 'this.scriptObj.setAttribute("src", this.fullUrl + this.noCacheIE);' in the JSONScriptRequest class?

<p>It sets the src attribute of the script tag to a new URL. (D)</p> Signup and view all the answers

Flashcards are hidden until you start studying

Study Notes

JavaScript ECMA Standard

  • Based on Netscape's JavaScript and Microsoft's JScript
  • Douglas Crockford is the original developer of JSON, now Senior JavaScript Architect at PayPal

JSON (JavaScript Object Notation)

  • A lightweight data interchange format
  • Allows loading data from a server or sending data to a server
  • Involves three steps: browser processing, server processing, and data exchange between them

JSON File

  • Can be loaded from the server or sent to the server
  • Can be operated upon by various programming languages (e.g., PHP, Java) using parsers
  • Can be converted into classes and attributes of the language

Client-Side (Browser)

  • JSON data is assigned to a variable, becoming an object in the program
  • Can be loaded from the server using XMLHttpRequest() or directly included in the HTML page

Server-Side

  • JSON file can be operated upon by various programming languages using parsers
  • Can be converted into classes and attributes of the language

Data Exchange

  • JSON data can be exchanged between the browser and server using XMLHttpRequest()
  • JSON file is sent as a text file and processed by the parser of the programming language

JSON and XMLHttpRequest

  • XMLHttpRequest can be used to load a JSON file from the server
  • XMLHttpRequest code: var req = new XMLHttpRequest(); req.open("GET", "file.json", true);
  • JavaScript callback: eval() parses JSON, creates an object, and assigns it to a variable

JSON eval() Function

  • Evaluates a string and executes it as if it was JavaScript code
  • Can be used to parse JSON data

Same Origin Policy

  • A security feature applied by browsers to client-side scripts
  • Prevents a document or script from getting or setting properties of a document from a different origin
  • Rationale: browsers should not trust content loaded from arbitrary websites

JSON Cross-Domain Hack

  • Uses JSON and the `

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

More Like This

Use Quizgecko on...
Browser
Browser