Web Technologies Lecture Week 3: Javascript Basics
25 Questions
0 Views

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 JavaScript as mentioned in the content?

  • To manipulate databases
  • To enhance server performance
  • To make webpages interactive (correct)
  • To compile programs

    • Which of the following statements about JavaScript scripts is true?

  • Scripts require special preparation before execution.
  • Scripts are written in plain text. (correct)
  • Scripts can only run in the browser.
  • Scripts need to be compiled before use.

    • Which JavaScript engine is used by Google Chrome?

  • V8 (correct)
  • ChakraCore
  • SpiderMonkey
  • Nitro

    • What does the console in JavaScript primarily serve as?

    <p>A debugging and evaluation tool</p> Signup and view all the answers

    When writing JavaScript within an HTML document, which tag should the script be wrapped in?

    &lt;script> Signup and view all the answers

    Which of the following is NOT a JavaScript engine mentioned?

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

    How is the browser’s debugging console categorized?

    <p>As an object of the browser</p> Signup and view all the answers

    What does REPL stand for in the context of the console?

    <p>Read, Evaluate, Print, Loop</p> Signup and view all the answers

    Which of the following is a method used to log output in the console?

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

    What keyword is used to declare a variable with a constant value in JavaScript?

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

    Which statement accurately describes the 'let' keyword?

    <p>It allows you to declare block scoped variables.</p> Signup and view all the answers

    What will the following code output if age is set to 16? var age = 16; if(age > 18){ console.log('Qualified for driving'); } else { console.log('Not qualified for driving'); }

    <p>Not qualified for driving</p> Signup and view all the answers

    Which of the following describes the scope of variables declared with 'var'?

    <p>They are always global scoped.</p> Signup and view all the answers

    What does the console.clear() method do?

    <p>It removes all prior messages from the console.</p> Signup and view all the answers

    In an if...else statement, what happens when the condition evaluates to false?

    <p>The else block executes.</p> Signup and view all the answers

    Which statement about 'const' variables is true?

    <p>They must be initialized when declared.</p> Signup and view all the answers

    What is the primary purpose of a switch statement in JavaScript?

    <p>To handle multiway branches efficiently based on a single variable.</p> Signup and view all the answers

    Which of the following is NOT a benefit of using a switch statement over multiple if...else if statements?

    <p>The flexibility to manage complex logical conditions.</p> Signup and view all the answers

    What will the output of the following code fragment be if the variable 'grade' is set to 'C'?

    var grade = 'C';
switch(grade){
 case 'A': console.log('Good Job');
 break;
 case 'B': console.log('Pretty Good');
 break;
 case 'C': console.log('Above Average');
 break;
 default: console.log('Marks not obtained');
}

    <p>Above Average</p> Signup and view all the answers

    In JavaScript loops, what is the role of the counter variable?

    <p>It controls the number of repetitions and keeps track of the current iteration.</p> Signup and view all the answers

    What type of loop is best suited for iterating a specific number of times in JavaScript?

    <p>For loop</p> Signup and view all the answers

    What will be the output of the following code if 'book' is 'science'?

    var book = 'science';
if(book == 'history'){
 console.log('Your book is history book.');
} else if(book == 'maths'){
 console.log('Your book is math book');
} else if(book == 'economics'){
 console.log('Your book is economics book');
} else{
 console.log('Your book is unknown');
}

    <p>Your book is unknown</p> Signup and view all the answers

    Which statement correctly describes the behavior of the break statement in a switch block?

    <p>It exits the switch block after the matched case and prevents fall-through.</p> Signup and view all the answers

    What type of loop would be most appropriate for iterating over each item in an array?

    <p>For loop</p> Signup and view all the answers

    Signup and view all the answers

    Study Notes

    Internet Software Architecture

    • This is a course, or lecture, on Internet Software Architecture.
    • Page 1 displays the course title alongside the institution logo.

    Web Technologies Lecture Week 3

    • This is a further lecture/course on Web Technologies—Week 3.
    • Page 2 displays the course title, week number, and topic—Introduction to Javascript.

    This Week's Agenda

    • Introduction to Javascript
    • Exploring the console
    • Declaring variables and functions
    • Conditional statements
    • Javascript loops
    • Understanding objects and arrays

    Introduction to Javascript

    • Javascript was created to make web pages interactive.
    • Javascript code is written as plain text.
    • Javascript programs can run when a webpage loads.
    • Javascript programs do not require special preparation or compilation.
    • Javascript can run in browsers, servers, or devices with a Javascript Engine.
    • Different Javascript engines have different codenames: (V8-Google Chrome & Opera, SpiderMonkey -Firefox, ChakraCore - Microsoft Edge, Nitro & SquirrelFish -Safari)
    • Understanding these engines is important for referencing developer articles.

    Introduction to Javascript

    • Javascript code can be written directly into the HTML document.
    • Or, written in a separate ".js" file; this is generally preferred.
    • If writing directly into HTML, it must be enclosed in a <script> tag.
    • Separate files do not require a <script> tag.

    Exploring the Console

    • The console is an in-browser tool used while coding with Javascript.
    • The console is a Read-Evaluate-Print-Loop (REPL).
    • It reads user input (Javascript code), evaluates it, and prints the result.
    • It allows repeated evaluation and input in a looped manner.
    • The console is used for debugging.

    Exploring the Console

    • The console is considered an object within the browser and can be used to access the browser's debug console.
    • Console objects function solely in the browser console; they do not function on pages.
    • Popular console methods include: console.log(), console.table(), and console.clear().

    Declaring Variables

    • Javascript variables can be declared using three keywords: var, let, and const
    • Each keyword defines a variable with different scopes.
    • var is a global scope variable.
    • let creates a block scope variable.
    • const defines a variable with a constant value.

    Declaring Variables Examples (var)

    • var is used as a global scope variable
    • The values of the variables declared using var can be modified.

    Declaring Variables Examples (let)

    • let is a block-scoped variable.
    • The values for variables declared with let can be modified.

    Declaring Variables Examples (const)

    • const is a block-scoped variable with a fixed value.
    • Any attempt to modify const variable will cause an error.

    Declaring Functions

    • Functions are the fundamental building blocks of Javascript programs.
    • A function is a set of instructions to perform a task or calculation.
    • Function declaration consists of: the function keyword, the name of the function, the parameter list, and the code block.
    • The return statement is used for returning values from functions.

    Declaring Functions: Return Value

    • Functions should always return a value (object, boolean etc).
    • When return is absent, a undefined value will be returned

    Conditional Statements

    • if statements specify a block of code for execution when a condition is true.
    • else statements specify code to be executed when the condition is false.
    • else if clauses allow for testing new conditions when prior conditions are false.
    • switch statements handle alternative code blocks based on different conditions for a single variable.

    If Statement Example

    • if statements execute conditionally based on a condition.

    If...Else Statement Example

    • if...else statements execute different code blocks based on whether a condition is true or false.

    If... Else If... Else Example

    • if...else if...else execute a series of conditional statements, testing different conditions.

    Switch Statement Examples

    • Multi-branching condition evaluations using switch statements.

    Javascript Loops

    • Javascript uses loops to repeat blocks of code.
    • for loops iterate a set number of times (based on counters)
    • for...in loops iterate over properties of objects
    • while loops iterate as long as a certain condition is true
    • do...while loops also iterate until a condition is fulfilled, but will always run at least once.

    Javascript Loop: For Example

    • for loops are used to execute code repeatedly.

    Javascript Loop: For...in Example

    • for...in loops, iterate through the properties of an object.

    Javascript Loop: While Example

    • while loops continue to execute as long as a condition is met.

    Javascript Loop: Do While Example

    • do...while loops execute at least once based on a condition being met.

    Javascript Objects

    • Objects in Javascript are similar to real-world objects (with properties and behaviours)
    • Objects in Javascript have properties (values) and methods (behaviours).
    • Javascript does not use classes like C++ or Java.
    • Objects are created directly and based on templates.
    • In javascript everything is an object, including variables with string values.

    Creating Javascript Objects

    • Objects can be created by defining properties and methods or using predefined properties and methods.
    • Three ways to create Javascript objects (Literal, Instance and Constructor Notation).

    Javascript Objects: Literal Notation Example

    • Simple way to create Javascript objects—useful for small programs.

    Javascript Objects: Instance of an Object Example

    • Creating new objects with the new keyword and the Object constructor.

    Javascript Arrays

    • Arrays are collections of homogeneous items, although javascript does not enforce homogeneity on the contents.
    • Javascript arrays store values contiguously in memory, unlike Java.
    • Arrays can contain a range of data types: strings, numbers, booleans, objects
    • Arrays' index starts from zero.

    Javascript Arrays: Literal Example

    • Demonstrates how arrays can be created with literals.

    Javascript Arrays: Instance Example

    • Illustrates instantiating arrays using the new Array() approach. (Similar to object creation example).

    Summary of Week 3 Lecture

    • This page lists the topics covered in week 3 of the course, linked to the specific slide within the presentation.

    What to Expect in Lab

    • The expectations for the practical lab sessions include revisions of Javascript basics, a first Javascript program exercise, and practical exercises building on the lecture content. Research is stressed.

    Before you come to Lab, Research!

    • These are topics to research/understand before the practical sessions.

    Studying That Suits You

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

    Quiz Team

    Related Documents

    JavaScript Lecture Week 3 PDF

    Description

    This quiz covers essential concepts from Week 3 of the Web Technologies course, focusing on Introduction to Javascript. You will explore the console, variables, functions, conditional statements, loops, and the fundamentals of objects and arrays in Javascript. Test your knowledge on the interactive features and functionalities that Javascript brings to web pages.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser