Module 6: Advanced JavaScript Features
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Questions and Answers

What is the primary purpose of a PHP script in the context of AJAX?

  • To execute JavaScript code
  • To style web pages
  • To process requests and interact with the database (correct)
  • To display HTML content on the client-side

The Fetch API is used to make HTTP requests in a similar manner as XMLHttpRequest.

True (A)

Name one example of a library that is used for data visualization.

Chart.js

The jQuery library is commonly used for ______ in web development.

<p>DOM manipulation</p> Signup and view all the answers

Match the following libraries with their primary functionality:

<p>jQuery = DOM manipulation axios = HTTP requests React = UI creation Chart.js = Data visualization</p> Signup and view all the answers

What is a key difference between libraries and frameworks?

<p>You can plug code into a framework, but must plug frameworks into your code. (B), Frameworks provide sections for plugging in code. (C)</p> Signup and view all the answers

All frameworks support both front-end and back-end development.

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

Name one example of a CSS framework.

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

A framework provides a ______ for how the developer's code should be structured.

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

Match the following programming languages with their corresponding back-end frameworks:

<p>PHP = Laravel Java = Spring Python = Django Ruby = Ruby on Rails</p> Signup and view all the answers

What is an important step to take when uploading files through PHP?

<p>Check the file type being uploaded (C)</p> Signup and view all the answers

The $_SESSION superglobal array is used to store data that can be accessed across different user sessions.

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

What is the purpose of using the enctype attribute in a file upload form?

<p>To specify how the form data should be encoded when submitted.</p> Signup and view all the answers

In PHP, session variables store data into a temporary file that is destroyed once the ________ is closed.

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

Match the following PHP terms with their descriptions:

<p>enctype = Specifies encoding type for form submission $_SESSION = Array storing session data file upload = Transferring files from client to server sql injection = A type of security vulnerability in queries</p> Signup and view all the answers

Which of the following statements about functions in JavaScript is true?

<p>Functions in JavaScript are first-class objects. (B)</p> Signup and view all the answers

A Promise in JavaScript is used to handle synchronous tasks.

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

What method is used to handle a fulfilled or resolved promise in JavaScript?

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

The syntax used to convert an object to a JSON string is ______.

<p>JSON.stringify</p> Signup and view all the answers

In JavaScript, anonymous functions can be expressed as:

<p>Arrow functions. (B)</p> Signup and view all the answers

Functions in JavaScript can only be named and cannot be anonymous.

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

What is the purpose of the resolve and reject arguments in a Promise?

<p>To handle the completion or failure of an asynchronous task.</p> Signup and view all the answers

What is the purpose of AJAX?

<p>To enable data exchange without reloading the webpage (B)</p> Signup and view all the answers

The XMLHttpRequest object is a newer innovation than the Fetch API.

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

What does the fetch() method return?

<p>A Promise</p> Signup and view all the answers

AJAX stands for Asynchronous JavaScript and ______.

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

What must occur to start a session for a user logging in?

<p>User credentials must match those stored in a database (B)</p> Signup and view all the answers

Which method is used to initiate the request in XMLHttpRequest?

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

Match the AJAX features with their definitions:

<p>asynchronous = Processes occur without interrupting user actions Promise object = Represents the completion of an asynchronous operation XMLHttpRequest = The original way to implement AJAX requests Fetch API = A modern method for making AJAX calls</p> Signup and view all the answers

Session variables can only be used after calling session_start().

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

What should be encoded if a user's login credentials do not match the database?

<p>an error message</p> Signup and view all the answers

The send() function can be called with an empty argument when using POST requests.

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

Sessions are stored on the ______, while cookies are saved on the user's ______.

<p>server-side, browser</p> Signup and view all the answers

Name one method that can be used to extract the message body from a Response object after a fetch() call.

<p>text() / json() / blob() / formData() / arrayBuffer()</p> Signup and view all the answers

Match the session-related terms with their descriptions:

<p>session_start() = Initiates or resumes a session session variables = Store user-specific data during a session logout.php = Script to destroy a user session HTTP cookies = Used for tracking or identifying returning users</p> Signup and view all the answers

Which statement about using prepared statements in login forms is true?

<p>They prevent SQL injection attacks. (C)</p> Signup and view all the answers

Cookies can be used to store data for general client-side purposes.

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

What happens to a session when a user logs out?

<p>the session is destroyed</p> Signup and view all the answers

Flashcards

AJAX

Asynchronous JavaScript and XML. A technique that allows web pages to update content without reloading the entire page, enhancing user experience.

PHP (in AJAX)

A server-side scripting language used to process requests from AJAX calls, often interacting with databases to retrieve and manipulate data.

Libraries

Collections of pre-written code, functions, and modules providing reusable components and tools to simplify web development.

jQuery

A popular JavaScript library that simplifies DOM manipulation, event handling, animation, and AJAX interaction.

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Fetch API

A modern, more robust way to interact with the web using a standardized API, allowing developers to make network requests without using third-party libraries.

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Library vs. Framework

A library provides components you can choose to use when needed, like a furniture store. A framework provides a structure you build within, like a house template.

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Front-end Frameworks

Frameworks for the user's side of a website, typically handling CSS and JavaScript, providing structure and functionality.

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Back-end Frameworks

Frameworks for the server side, handling logic, databases, and communication, often specific to programming languages.

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Preprocessors

Tools that translate simpler code into another format (like CSS or JavaScript) for browsers to understand.

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Vanilla code

Plain, unprocessed code written without any frameworks or libraries, often used for basic functionality.

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First-class Objects

Functions in JavaScript are treated as first-class objects. This means they can be assigned to variables, passed as arguments to other functions, and returned as values from functions.

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Anonymous Functions

Functions without a name. They are often used as arguments to other functions or to create closures.

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Arrow Functions

A concise syntax for writing anonymous functions. They are often preferred in modern JavaScript for their shorter and more expressive code.

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JSON: JavaScript Object Notation

A human-readable format for exchanging data between systems. It uses a key-value pair structure.

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JSON.stringify()

Converts a JavaScript object into a JSON string. Useful for sending data over the network.

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JSON.parse()

Parses a JSON string and converts it into a JavaScript object. Used to receive data from a network.

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Promise

An object representing the eventual completion or failure of an asynchronous operation. It holds the result of an operation, but you don't get it immediately.

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Promise.then()

A method to handle the successful completion (fulfillment) of a Promise. Allows you to specify code to run when the Promise resolves.

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XMLHttpRequest (XHR)

An object used in early AJAX implementations to send and receive data from servers. It handles the process of communication.

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Callback Function

A function that executes after an asynchronous task is complete, allowing for dynamic updates based on received data.

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Open() method in XHR

Defines the HTTP method (GET, POST) of the request, essentially telling the server what action to perform.

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Send() method in XHR

Initiates the data transfer to or from the server, carrying out the specific requested action.

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Fetch() method

Specifies the URL of the resource to access and sends the request to the server.

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POST Requests with Fetch API

Allows sending data to the server in the body of the request, often used for form submissions or data updates.

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Enctype Attribute

The 'enctype' attribute in HTML forms specifies how form data should be encoded when it is submitted to the server. For file uploads, it must be set to 'multipart/form-data' to allow the transmission of binary data.

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File Upload with PHP

File uploads in PHP involve receiving the uploaded file from the client, processing it (checking file type, size, etc.), and storing it on the server. This typically involves handling the $_FILES superglobal array and using functions like move_uploaded_file() to manage the uploaded file.

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Session Handling with PHP

Sessions in PHP allow web applications to store user-specific data between requests. This data is maintained in the $_SESSION superglobal array and usually persists in a temporary file on the server until the session is closed.

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Session Variables

Session variables are data stored within the $_SESSION array. This data is associated with a specific user during their session and persists across multiple requests.

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SQL Injection Vulnerability

SQL injection is a security risk where malicious code (SQL commands) is injected into data submitted to a web application. If the application's code doesn't properly sanitize user input, attackers can manipulate databases, potentially causing data leaks or even system access.

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Session Handling

A process used to maintain user data and state across multiple requests from the same browser. It allows information about a user, such as login status and preferences, to be stored on the server-side and accessed in subsequent requests.

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Login Form Validation

The process of checking if a user's entered credentials (like username and password) match the database information. It aims to prevent unauthorized access and ensure security.

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Prepared Statements

A safer way to execute database queries by preventing SQL injection vulnerabilities. Parameters are passed separately, preventing malicious code from entering the database.

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Session Start

The function that initiates or resumes a PHP session. It creates a unique session ID and sets up a dedicated space for storing session variables.

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Session Destruction

The process of ending a user's session, clearing all session data and invalidating the session ID. It effectively logs the user out.

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HTTP Cookies

Small pieces of data sent from a web server to a user's browser, allowing the server to store and retrieve information about the user. They can be used for tracking preferences, login status, and personalized content.

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Web Storage API (localStorage and sessionStorage)

Modern web storage APIs for storing key-value pairs in the browser. localStorage persists data across sessions, while sessionStorage retains data only for the current session.

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Study Notes

Module 6: Additional Scripting Features

  • This module covers advanced JavaScript scripting, including first-class functions, asynchronous features, and object manipulation.

Objectives

  • Discuss how functions are first-class objects in JavaScript.
  • Utilize functions as well as other relevant Javascript features (Promise, fetch, etc.) in web applications.
  • Apply techniques for asynchronous JavaScript and XML (AJAX).

Functions in JS

  • Functions are first-class objects in JavaScript, allowing flexibility in coding.
  • Functions can be stored in variables.
  • Functions can be part of arrays.
  • Functions can be passed as arguments to other functions.
  • Functions can serve as the return value of a function.
  • Functions can be defined as expressions and assigned to variables.
  • Functions can be named or anonymous.
  • Anonymous functions can be expressed as arrow functions.

User-defined Objects

  • JavaScript uses new Object() to create objects.
  • Objects are collections of properties and methods.
  • Properties store data, and methods are functions contained within the object.
  • Accessing properties: person.name or person['name'].
  • Object literals: var subject = {};
  • Object literals allow defining properties directly within the object.
  • Object constructors: function Student (idno, name, course, year)
    • Use the new keyword to create objects.
    • this keyword refers to the current object.
    • prototype.toString creates a method accessible on all object instances.

JSON

  • JavaScript Object Notation (JSON) is a text syntax for storing and exchanging data among applications.
  • JavaScript allows converting JSON-formatted strings to objects, and vice-versa.
    • JSON.stringify(objecttype) converts a JavaScript object to a JSON string.
    • JSON.parse(stringtype) converts a JSON string to a JavaScript object.

Promise

  • A Promise represents the eventual completion or failure of an asynchronous task (e.g. network request).
  • A promise contains a value which is made available to the user at a later time.
  • Promises are instantiated with a function that takes resolve and reject as arguments.
    • resolve is called when the operation succeeds.
    • reject is called when the operation fails.
    • .then() is used to handle a fulfilled (successful) promise.
    • .catch() is used to handle a rejected (failed) promise.

AJAX

  • Asynchronous JavaScript and XML (AJAX) is a set of techniques that allow for interactions with a server without requiring a full page reload.
  • AJAX techniques typically use XMLHttpRequest or the Fetch API to make requests to a server and get updated or new data sent to the client-side.

AJAX & PHP

  • Use Javascript's XMLHttpRequest or Fetch API to send asynchronous requests to a PHP script on the server.
  • The PHP script processes the request and returns a response back to the client (JavaScript).

Libraries

  • A collection of utilities and functions.
  • Can be for specific needs.
  • Functions/modules in a library can be reused, which may save time.
    • Examples: jQuery, jQuery UI, React, Validator, Pristine, Chartist.js, and more.

Frameworks

  • A framework provides a structure or template for building applications.
  • Developers plug their specific code into the framework.
  • Front-end frameworks use JavaScript and/or CSS to handle the client part of the application.
    • Examples: Angular, Vue.js, Ember.js, Semantic UI, Next.js
  • Back-end frameworks handle server logic, often using specific server-side languages.
    • Examples: Laravel, Symfony, CodeIgniter, Yii, Zend (PHP); Spring, Struts, Grails, DropWizard (Java); Express, DerbyJS, Koa, Meteor (Node.js); Django, Pyramid, Flask (Python); Ruby on Rails (Ruby)

Handling File Uploads with PHP

  • Enable file uploads in your PHP configuration.
  • Use a form with enctype="multipart/form-data" to handle file uploads.
  • Retrieve the uploaded file data using $_FILES.
  • Ensure correct error handling for upload failures.
  • Manage file naming to avoid conflicts.
  • Move the uploaded file securely to a designated directory.

Session Handling with PHP

  • Session handling in PHP allows you to manage user data across multiple requests within a single browser session.
  • Store data in the $_SESSION array to maintain state between requests.
  • The session starts with session_start();.
  • The session_unset() function clears all session variables for a specific user.
  • session_destroy() deletes the session.

Cookies in PHP

  • Cookies in PHP are used to store data on the client's machine (browser).
  • Cookies provide a way to maintain information about a user across multiple visits to a website. -Use session_start().

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Module 6: Additional Scripting Features PDF

Description

This quiz focuses on advanced JavaScript concepts, including first-class functions, asynchronous programming, and object manipulation. Explore how these features enhance web applications and their practical applications. Test your understanding of concepts like Promises and AJAX in JavaScript.

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