Questions and Answers
What is the primary purpose of using 'use strict'; in the script?
What does the pop method do to an array?
What is the correct result of data.unshift(0) given const data = [1, 2, 3];?
Which of the following statements about function expressions is true?
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Which of the following correctly retrieves the last name of Moge?
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What will the console.log statement for introduction.firstName return?
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What does indexOf do in the context of array methods?
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Which statement accurately describes how arrow functions differ from regular function declarations?
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What does the 'unshift' method do when applied to an array?
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In the context of JavaScript, what is a primary characteristic of an object?
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How does strict mode enhance JavaScript programming practices?
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What is a key use case for nested functions in JavaScript?
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What is true about function expressions as compared to function declarations?
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When using literal notation to create an array, which of the following is correct?
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In JavaScript, what does the 'push' method do to an array?
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What is a typical use case for Node.js in JavaScript development?
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What will the return value of the method introduction.calcAge(2023) be?
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What is the data type of the friends property in the introduction object?
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What will be the output of console.log(introduction.calcAge(2024))?
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Which method is used to compute Moge's age in the introduction object?
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Study Notes
JavaScript Strict Mode
- Strict mode improves security and error detection in JavaScript.
- Declared using
'use strict';at the beginning of scripts.
Functions in JavaScript
-
Function Declaration: Uses the
functionkeyword. Example:-
function calcTwoNumbers(firstNumber, secondNumber)
-
- Returns the product of two numbers.
-
Function Expression: Expressions can create functions, assigned to variables.
- Example:
const mySecondFunction = function(firstNumber, secondNumber) { return firstNumber * secondNumber; }
- Example:
-
Arrow Functions: A shorter syntax for functions.
- Example:
const anArrowFunction = (a, b) => a * b;
- Example:
Functions Calling Other Functions
-
Nested Functions: Functions can call other functions.
- Example:
cutFruitfunction cuts a fruit into pieces, then used infruitProcessorto process apples and oranges.
- Example:
- Returns a string summarizing the operation.
Arrays in JavaScript
- Creation: Using literal notation or the
Arrayconstructor.- Example using literal:
const data = [1, 2, 3]; - Example using constructor:
const dataTwo = new Array('a', 'b', 'c');
- Example using literal:
- Array Methods:
-
push: Adds an element to the end. Example:
data.push(4) -
pop: Removes the last element. Example:
data.pop() -
unshift: Adds an element to the start. Example:
data.unshift(0) -
shift: Removes the first element. Example:
data.shift()
-
push: Adds an element to the end. Example:
- Array Manipulation: Includes checking for elements with
indexOfandincludes.
Objects in JavaScript
- Objects are collections of properties and methods.
- Example:
const introductioncontains personal information with properties like first name, last name, and birth year. - Methods: Functions defined within an object that operate on its properties.
- Example:
calcAgecalculates age based on the current year.
- Example:
Logging and Retrieving Properties
- Accessing object properties directly using dot notation.
- Example:
introduction.firstName
- Example:
- Retrieving multiple properties can be done using array syntax.
- Example:
console.log([introduction.firstName, introduction.lastName]);
- Example:
Node.js Context
- Node.js allows server-side JavaScript execution, handling I/O operations, and providing backend services.
- The concepts presented are foundational for both frontend and backend JavaScript development, emphasizing function and array manipulation.
JavaScript Strict Mode
- Strict mode enhances security and error detection within JavaScript code.
- Activated by adding
'use strict';at the beginning of scripts or functions.
Functions in JavaScript
-
Function Declaration: Uses the
functionkeyword to define functions.- Example:
function calcTwoNumbers(firstNumber, secondNumber)returns the product of two numbers.
- Example:
-
Function Expression: Functions can be defined within expressions and assigned to variables.
- Example:
const mySecondFunction = function(firstNumber, secondNumber) { return firstNumber * secondNumber; }
- Example:
-
Arrow Functions: Provide a concise syntax for defining functions.
- Example:
const anArrowFunction = (a, b) => a * b;
- Example:
Functions Calling Other Functions
- Functions can call other functions, leading to nested structures.
- Example: The
cutFruitfunction can be used infruitProcessorto process apples and oranges, returning a summary string.
- Example: The
Arrays in JavaScript
-
Creation: Can be created using literal notation or the
Arrayconstructor.- Literal:
const data = [1, 2, 3]; - Constructor:
const dataTwo = new Array('a', 'b', 'c');
- Literal:
Array Methods
-
push(): Adds an element to the end of the array.- Example:
data.push(4);
- Example:
-
pop(): Removes the last element from the array.- Example:
data.pop();
- Example:
-
unshift(): Adds an element to the start of the array.- Example:
data.unshift(0);
- Example:
-
shift(): Removes the first element from the array.- Example:
data.shift();
- Example:
- Array manipulation also includes methods like
indexOfandincludesfor checking the existence of elements.
Objects in JavaScript
- Objects are collections of properties and methods, encapsulating related data and functions.
- Example:
const introductioncontains properties such as first name, last name, and birth year.
- Example:
-
Methods: Functions defined within an object that operate on its properties.
- Example:
calcAgecalculates age using the current year.
- Example:
Logging and Retrieving Properties
- Access object properties using dot notation.
- Example:
introduction.firstNameretrieves the first name.
- Example:
- Multiple properties can be retrieved with array syntax.
- Example:
console.log([introduction.firstName, introduction.lastName]);
- Example:
Node.js Context
- Node.js enables server-side JavaScript execution, facilitating I/O operations and backend services.
- Understanding these JavaScript concepts is essential for both frontend and backend development, especially in function and array manipulation.
Object Structure
- Represents an object named
introduction. - Contains various key-value pairs that describe a person.
Properties
-
firstName: Assigned the value 'Moge'. -
lastName: Assigned the value 'Okulaja'. -
birthYear: Set to 1999, indicating the year of birth. -
job: Defined as 'Software Engineer', indicating professional occupation. -
friends: Array containing names ['Ella', 'Lilian', 'Asma', 'Madiss'], showcasing personal relationships.
Object Methods
-
calcAge: A function that calculates age based on the current year provided as an argument.- Uses
currentYearto subtractbirthYearfor age calculation. - Returns a string: "Moge is X years old", where X is the calculated age.
- Uses
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Description
This quiz covers key concepts of JavaScript functions, including function declarations, expressions, and arrow functions. It also explores the role of strict mode in enhancing security and functionality in JavaScript. Prepare to test your knowledge on how these features work together.
