JavaScript with Node.js

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Questions and Answers

What is the output of the following code: `let student = {name: 'John', age: 20, major: 'CS'}; for (let prop in student) { console.log(prop + ': ' + student[prop]); }`

name: John, age: 20, major: CS (correct)

Error: prop is not defined

name, age, major

John, 20, CS

What is the purpose of the `while` loop in the following code: `let i = 0; while (i < 5) { console.log(i); i++; }`

To define a function

To iterate over an array

To execute a block of code repeatedly until a condition is met (correct)

To declare a variable

What is the difference between a function declaration and a function expression?

A function declaration is used to define a function, while a function expression is used to call a function.

A function declaration is used to define a function with a return type, while a function expression is used to define a function without a return type.

A function declaration is used to define a function with a name, while a function expression is used to define a function without a name.

A function declaration is used to define a function, while a function expression is used to define a function as a value. (correct)

What is the purpose of the `rest parameter` syntax in JavaScript?

To define a function with a variable number of arguments Signup and view all the answers

What is the output of the following code: `let greet = function(name) { return 'Hello, ' + name; }; console.log(greet('John'));`

Hello, John Signup and view all the answers

What is the difference between `let` and `const` in JavaScript?

let is used to declare a variable, while const is used to declare a constant Signup and view all the answers

What is the purpose of the `for...in` loop in the following code: `let student = {name: 'John', age: 20, major: 'CS'}; for (let prop in student) { console.log(prop + ': ' + student[prop]); }`

To iterate over the properties of an object Signup and view all the answers

What is the output of the following code: `let i = 0; do { console.log(i); i++; } while (i < 5);`

0, 1, 2, 3, 4 Signup and view all the answers

What is the purpose of arrow functions in JavaScript?

To define a function with a shorter syntax Signup and view all the answers

What is the difference between `console.log()` and `return` in JavaScript?

console.log() is used to log a message to the console, while return is used to exit a function Signup and view all the answers

Study Notes

Node.js and JavaScript Basics

Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine, allowing JavaScript to run on servers or laptops.
Node.js can be installed from https://nodejs.org/.
Running Node.js interactive shell: open terminal, type node, and press Enter.
JavaScript code can be entered in the interactive shell and executed immediately.

JavaScript Console Example

Example of using JavaScript console:
- Declare a variable: let x = 10;
- Log the variable: console.log(x);
- Perform arithmetic operations: x + 5;
- Declare a string variable: let y = 'Hello, world!';
- Convert string to uppercase: y.toUpperCase();

JavaScript Basics

JavaScript has only seven primitive types, which are not objects and have no methods:
- Undefined (a variable that has not been assigned a value)
- Null (represents the intentional absence of any object value)

Required Reading

Required reading for JavaScript: "JavaScript Crash Course" by Nick Morgan, "Part I: The Language"

JavaScript, HTML, and CSS

JavaScript:
- Is an object-oriented programming language
- Runs in web browsers
- Can be used to design/program web page behavior
HTML (Hyper Text Markup Language):
- Standard markup language for creating web pages
- Describes web page structure
CSS (Cascading Style Sheets):
- Style sheet language for describing web page look and formatting
- Provides visual aspects of web pages

Browser Consoles

Browser consoles allow writing and executing JavaScript code on the fly
Example of using browser console:
- Declare an object: let student = {name: 'John', age: 20, major: 'CS'};
- Use for...in loop to iterate over object properties

Conditionals and Loops

Examples of while and do-while loops:
- While loop: while (i < 5) { console.log(i); i++; }
- Do-while loop: do { console.log(j); j++; } while (j < 15);

Functions

Functions can be defined:
- Using function declarations: function greet1(name) { ... }
- Using function expressions: const greet2 = function(name) { ... }
- Using arrow functions: const greet3 = (name) => { ... }
Rest parameter syntax allows functions to accept any number of arguments as an array.

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Description

Learn about using Node.js to run JavaScript on your server or laptop. Discover how to install Node.js and start the interactive shell.