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;
console.log();
console.log(`Found ${office0}`);
console.log();

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