Learn JavaScript

# Run these commands to create a new project
mkdir myproject
cd ./myproject
npm init # Follow the prompts; using defaults is fine the package.json file can be edited later.

const color = {
    END      : '\033[0m',
    BOLD_UNDERLINE : '\033[1m\033[4m'
}

console.log(`${color.BOLD_UNDERLINE}Assign a string value to a variable${color.END}`)
console.log()
const office_name1 = 'Office A'
console.log(office_name1)
console.log()
console.log("----------------------------------------------")
console.log()

console.log(`${color.BOLD_UNDERLINE}Assign a multiple line string value to a variable${color.END}`)
console.log()
const office_name2 = `Office A\n
Office B
`
console.log(office_name2)
console.log("----------------------------------------------")
console.log()

console.log(`${color.BOLD_UNDERLINE}Assign an integer value to a variable${color.END}`)
console.log()
const office_sales = 7
const office_sales_type = typeof(office_sales)
console.log(`office_sales is a lucky ${office_sales_type} ${office_sales}`)
console.log()
console.log("----------------------------------------------")
console.log()

console.log(`${color.BOLD_UNDERLINE}Assign an boolean value to a variable${color.END}`)
console.log()
office_is_active = true
office_is_active_type = typeof(office_is_active)
console.log(`office_score is a ${office_is_active_type} ${office_is_active}`)
console.log()
console.log("----------------------------------------------")
console.log()

// A simple single-line comment
console.log("There's a comment before this line, trust me.")
/*
A
Comment
on multiple lines
*/
console.log()
console.log("A few comments just happened, honest!")
console.log()

/**
 * Represents a book.
 * @constructor
 */
function Book(title, author) {
}
console.log("Look at the code to see what a JSDoc comment looks like.")
console.log("What is JSDoc? https://jsdoc.app/about-getting-started.html")

const colors = {
  END: '\033[0m',
  BOLD_UNDERLINE: '\033[1m\033[4m'
}

/*
The if statement executes a statement if a specified condition is truthy. If the condition is falsy, another statement can be executed.
*/
console.log(`${colors.BOLD_UNDERLINE}An if statement.${colors.END}`)
console.log()
if(true) {
  console.log("Since true is true this line prints.")
}
console.log()
console.log('-----------------------')
console.log(`${colors.BOLD_UNDERLINE}An if else statement.${colors.END}`)
console.log()
if(false) {
  // I won't do anything, I refuse!
} else {
  console.log('Since false is false this line prints.')
}
console.log()
console.log('-----------------------')

/*
The for statement creates a loop that consists of three optional expressions, enclosed in parentheses and separated by semicolons, followed by a statement (usually a block statement) to be executed in the loop.
*/
console.log(`${colors.BOLD_UNDERLINE}A standard for loop.${colors.END}`)
console.log()

offices = ["Office A", "Office B", "Office C"]

for (var i = 0; i < offices.length; i++) {
  console.log(`${offices[i]}\n`)
}
console.log()
console.log('-----------------------')
/*

The purpose of the for-in statement is to enumerate over object properties. The for in statement reads up the prototype chain and enumerates over inherited properties.

*/
console.log(`${colors.BOLD_UNDERLINE}Use for in to loop over the properties of the color object.${colors.END}`)
console.log()
console.log()
for (color in colors) {
  console.log(`${color}\n`)
}
console.log()
/*
The purpose of the forEach function is to
enumerate the elements of an array. Using a forEach
function prevents out of bounds errors that can occur when using a for loop with an index. If you need to break from your loop avoid the use of forEach.
*/
console.log('-----------------------')
console.log(`${colors.BOLD_UNDERLINE}Create an orderly bounded and scoped loop with the .forEach function.${colors.END}`)
console.log()
console.log()
const numbers1 = [1, 2, 3, 4, 5];

let txt = "";
numbers1.forEach(myFunction)

function myFunction(value, index, array) {
  console.log(txt += value)
}

console.log()
/*
The for of statement is used for looping over
iterable objects like arrays, maps, sets, Etc.
*/
console.log('-----------------------')
console.log(`${colors.BOLD_UNDERLINE}Create an orderly loop with the for of statement.${colors.END}`)

const numbers2 = [1, 2, 3, 4, 5];
console.log()

for (let value of numbers2) {
  console.log(value);
}

/*
A while statement executes its statements as long as a specified condition evaluates to true.
*/
console.log('-----------------------')
console.log(`${colors.BOLD_UNDERLINE}Create a while loop that loops until a condition if met.${colors.END}`)
console.log()
i = 0
while (i < 5) {
  i++;
  console.log(i)
}
console.log('-----------------------')

/*
The do...while statement creates a loop that executes a specified statement until the test condition evaluates to false.

The only difference between do while and a while loop is that at least one execution will occur since the evaluation executes after enclosed statement(s).
*/
console.log('-----------------------')
console.log(`${colors.BOLD_UNDERLINE}Create a do while loop that loops until a condition is met.${colors.END}`)
console.log()
i = 0
do {
  i++;
  console.log(i)
} while (i < 5)

const color = {
    END      : '\033[0m',
    BOLD_UNDERLINE : '\033[1m\033[4m'
}

console.log(`${color.BOLD_UNDERLINE}Create a function then execute it.${color.END}`)
console.log()
function myFunction() {
  console.log('Executed myFunction')
}
myFunction()

console.log("----------------------------------------------")
console.log()
console.log(`${color.BOLD_UNDERLINE}Create an arrow function then execute it.${color.END}`)
console.log()
myArrowFunction = () => {
  console.log('Executed myArrowFunction')
}
myArrowFunction()
console.log()
console.log("----------------------------------------------")
console.log()
console.log(`${color.BOLD_UNDERLINE}Create a function as an expression then execute it.${color.END}`)
console.log()
const myExpressionFunction = function() {
  console.log('Executed myExpressionFunction')
}
myExpressionFunction()
console.log()
console.log("----------------------------------------------")
console.log()
console.log(`${color.BOLD_UNDERLINE}Create a function with the Function constructor then execute it.${color.END}`)
console.log()
const myFunctionConstructorFunction = Function('console.log("Executed myFunctionConstructorFunction")')
myFunctionConstructorFunction()
console.log()
console.log("----------------------------------------------")
console.log()

const color = {
  END: '\033[0m',
  BOLD_UNDERLINE: '\033[1m\033[4m'
}

/*

https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Objects/Basics

An object is a collection of related data and/or functionality (which usually consists of several variables and functions — which are called properties and methods when they are inside objects.) Let's work through an example to understand what they look like.

*/
console.log(`${color.BOLD_UNDERLINE}Create a new JavaScript object.${color.END}`)
console.log()
const officeObject = {
  name: 'officeObject'
}
console.log(officeObject)
console.log()
console.log(`${color.BOLD_UNDERLINE}Access the value of officeObject.name.${color.END}`)
console.log()
console.log(officeObject.name)
console.log('------------------------------')
console.log()
/*

https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Objects/Object_prototypes

Prototypes enable object inheritance in JavaScript

JavaScript is often described as a prototype-based language — to provide inheritance, objects can have a prototype object, which acts as a template object that it inherits methods and properties from.

*/
console.log(`${color.BOLD_UNDERLINE}Create constructor function, instantiate it, then call a method on it.${color.END}`)
console.log()
function OfficeConstructorFunction(name) {
  this.name = name
}

OfficeConstructorFunction.prototype.open = function() {
  console.log(this.name + ' has opened for business!');
};

const officeConstructorFunction = new OfficeConstructorFunction("officeConstructorFunction")
console.log(officeConstructorFunction)
console.log(officeConstructorFunction.open())
console.log('------------------------------')
/*
ECMAScript 2015 Classes have simplified the
classic prototype syntax. Use this syntax to make your code easier to read.
*/
console.log(`${color.BOLD_UNDERLINE}Create a class, instantiate it, then call a method on it.${color.END}`)
console.log()
class OfficeECMA2015Class {
  constructor(name) {
    this.name = name
  }

  open() {
    console.log(`${this.name} has opened for business!`)
  };
}

const officeECMA2015Class = new OfficeECMA2015Class('officeECMA2015Class')
console.log(officeECMA2015Class)
officeECMA2015Class.open()
console.log('------------------------------')

const fs = require('fs')

const color = {
  END: '\033[0m',
  BOLD_UNDERLINE: '\033[1m\033[4m'
}

console.log(`${color.BOLD_UNDERLINE}Try to read an existing file and finally make it!${color.END}`)

const read_file = (fileName) => {
  let fileContents;
  try {
    fileContents = fs.readFileSync(fileName, 'utf8');
  } catch (err) {
    if (err.code === 'ENOENT') {
      console.log(`Missing file: ${fileName}`);
    } else {
      throw err;
    }
  } finally {
    console.log()
    console.log("I finally made it!")
  }
  return fileContents
}

console.log()
const fileContents = read_file('example.csv')
console.log()
console.log('fileContents:', fileContents)
console.log('-----------------------')
console.log()

console.log(`${color.BOLD_UNDERLINE}Read a non-existent file and catch the exception.${color.END}`)
console.log()

read_file('missing_file.csv')
console.log('-----------------------')

const color = {
  END: '\033[0m',
  BOLD_UNDERLINE: '\033[1m\033[4m'
}

console.log(`${color.BOLD_UNDERLINE}Create an office array.${color.END}`)
console.log()

const offices = ["Office A","Office B", "Office C"]

console.log(`We have an office array: ${offices}`)
console.log()
console.log(`Accessing array item 0`)
office0 = offices[0]
console.log()
console.log(`Found ${office0}`)
console.log()

console.log('Update an array value')
console.log()
offices[0] = "Office Z"
console.log(`Updated Office A to ${offices[0]}`)
console.log()

console.log('Get the length of the array')
console.log()
offices_length = offices.length
console.log(`${offices_length} offices exist in the array`)
console.log()

console.log("Loop a sorted array")
console.log()
for(office of offices.sort()) {
  console.log(office)
}
console.log()

console.log('Add an array element named Office Y')
offices.push("Office Y")
console.log(offices)
console.log()

console.log('Remove the first element of an array')
offices.splice(0, 1)
console.log(offices)
console.log()

const color = {
  END: '\033[0m',
  BOLD_UNDERLINE: '\033[1m\033[4m'
}

console.log(`${color.BOLD_UNDERLINE}Arithmetic Operators${color.END}`)
console.log()
const addition = 1 + 1
console.log(`1 + 1 = ${addition}`)
console.log()

const subtraction = 2 - 1
console.log(`2 - 1 = ${subtraction}`)
console.log()

const multiplication = 3 * 3
console.log(`3 * 3 = ${multiplication}`)
console.log()

const exponentiation = 2 ** 3
console.log(`2 ** 3 = ${exponentiation}`)
console.log()

const division = 10 / 5
console.log(`10 / 5 = ${division}`)
console.log()

const modulus = 6 % 3
console.log(`6 % 3 = ${modulus}`)
console.log()

let increment = 1
increment++
console.log(`1++ = ${increment}`)
console.log()

let decrement = 1
decrement++
console.log(`1++ = ${decrement}`)
console.log()


console.log(`${color.BOLD_UNDERLINE}Assignment Operators${color.END}`)
console.log()

let equals = 1
console.log(`1 = ${equals}`)
console.log()

equals += 1
console.log(`1 += ${equals}`)
console.log()

let minus_equals = 2
minus_equals -= 1
console.log(`2 -= ${minus_equals}`)
console.log()

let multiply_and = 5
multiply_and *= 5
console.log(`5 *= ${multiply_and}`)
console.log()

let divide_and = 5
divide_and /= 5
console.log(`5 /= ${divide_and}`)
console.log()

let modulus_and = 6
modulus_and %= 3
console.log(`6 %= ${modulus_and}`)
console.log()

exponent_and = 2
exponent_and *= 3
console.log(`2 *= ${exponent_and}`)
console.log()

exponent_assign = 2
exponent_assign **= 3
console.log(`2 **= ${exponent_assign}`)
console.log()