Variables 

    - declare JavaScript variables with var, let or const. 
    - If the value of the variable can change, like a total, use let. If the value is set, like prices, use const. Variables can hold any data type. 
var x = 5;
var y = 6;
var z = x + y;

z

11

Data types- there are 8 JS data types.

  • List a few data types that you already know

    integer string boolean

1. String: a series of characters, written with single or double quotes 

let text = "Mort";
text

'Mort'
let text2 = 'Yeung';
text2

'Yeung'

2. Number: can be integers or decimals. 

    - You can also have exponential notation for large/small numbers

3. Bigint: used to store integer values that are too big to be represented by a normal JS number 

    - JavaScript integers are only accurate up to 15 digits
let number = 1234567890123456789012345n;
let Largenum = BigInt(1234567890123456789012345)

let typeLargenum = typeof Largenum;
typeLargenum

'bigint'
Largenum

1234567890123456824475648n

4. Boolean: true or false, used in conditional testing 

Boolean(10 > 9)

false

Write a boolean statement that outputs true

5. Undefined: a variable without a value, has the value undefined/empty values 

let name;  
name

grade = undefined;

6. Null: represents the intentional absence of any object value 

    - variable is empty at the moment and may have a value later
let result;

result = Boolean(undefined);
console.log(result); // false

result = Boolean(null);
console.log(result); // false

false
false

7. Symbol: used to represent unique values that can be used as identifiers/keys in objects. 

    - They are also used to create private properties and methods in classes.
    - unique and immutable, so they can be used as unique identifiers in objects and classes.
    - useful for creating constants that can be shared across different parts of your code.
// Create a Symbol
const mySymbol = Symbol();

console.log(mySymbol);
// expected output: Symbol()

Symbol()

const myObject = {
    [mySymbol]: 'Hello World'
  };
  
  console.log(myObject[mySymbol]);

Hello World

Edit/add to the code above so that it outputs "Hello World"

8. Object: an unordered collection of key-value pairs. Each key-value pair is called a property. 

    - object: written with curly braces {}, name:value pairs
    - array: written with square brackets, separated by commas

Object

  • Identify the name/keys in the object below: name, breed, color, age
  • Identify the values in the object below: Elly, Rottweiler, black, 4
const dogs = {name: "Elly", breed:"Rottweiler", age:4, color:"black"}
dogs

{ name: 'Elly', breed: 'Rottweiler', age: 4, color: 'black' }

Array

const songs = ["Love Story", "Blank Space", "I Knew You Were Trouble"];
songs

[ 'Love Story', 'Blank Space', 'I Knew You Were Trouble' ]

Const 

    - We use const to declare variables whose value can be initialized only at the time of declaration.  
    - Const means that the identifier cannot be reassigned. 
const cost1 = 2;
const cost2 = 11;
let totalCost = cost1 + cost2;

totalCost

13

Conditionals: control behavior, decides whether or not pieces of code can run. 

- If: if a condition is true it is used to specify execution for a block of code.
- Else: if the same condition is false it specifies the execution for a block of code.
- Else If: new test if the first condition is false.
if (10 > 5) {
    var outcome = "True";
}

outcome;

'True'
if ("red" === "blue") {
    var outcome = "if block";
} else {
    var outcome = "else block";
}
outcome;

'else block'
let temperature = 54
if (temperature < 70) {
    cast = "Chilly";
  } else if (temperature < 60) {
    cast = "Cold";
  } else {
    cast = "Warm";
  }

cast

'Chilly'

Create a conditional statement about how you would greet someone based on the time of day.

let currentTime = 5
if (currentTime < 70) {
    greeting = "Good morning!";
  } else if (temperature < 60) {
    greeting = "Good afternoon!";
  } else {
    greeting = "Good evening!";
  }

  greeting

'Good morning!'

Functions: 

- defining: define with function + functionName(parameter) { function code }.  It can be unnamed/anonymous can be defined based on a condition.
- calling: simply put the function name with a parameter and semicolon, or a function can call itself (recursive)

Iteration: 

    - for loop: repeats until a specified condition evaluates to false
    - do...while: repeats until a specified condition evaluates to false
    - while statement: executes its statements as long as a specified condition evaluates to true
    - label: provides a statement with an identifier that lets you refer to it later in the code. ex. you can use a label to identify a loop, and then use the break or continue statements to    indicate whether a program should interrupt the loop or continue its execution
    - break: used to terminate a loop, switch, or in conjunction with a labeled statement
    - continue: can be used to restart a while, do-while, for, or label statement
    - for...in: iterates a specified variable over all the enumerable properties of an object
    - for...of statement creates a loop Iterating over iterable objects, invoking a custom iteration hook with statements to be executed for the value of each distinct property

JavaScript in HTML- Questions

  1. Where do you store the JavaScript Code?
  • I store Javascript code in .js file
  1. How do you import a JS file into HTML?
  • < script src="name.js"></ script>
  1. What is onClick?
  • onClick describes a function in which a click happens, some action occurs
  1. What tag do you use to write JavaScript code?
  • use < script > tag

Hacks

  1. Add notes in this notebook
  2. Complete the code portions, questions, and prompts throughout the notebook
  3. Extra Credit: code a small JavaScript game

Javascript Hangman Game

(Link)[https://jonathanwuz.github.io/LeuckACheuck/]

  • This is a hangman Javascript game code through html and javascript. The Submit button is colorful and is apart of the SASS hacks.

JS Code: 

<script>
    // Initialize variables
    var words = ["apple", "banana", "cherry", "date", "elderberry", "fig", "grape", "honeydew", "indian gooseberry", "jackfruit", "kiwi", "lemon", "mango", "nectarine", "orange", "peach", "quince", "raspberry", "strawberry", "tangerine", "ugli fruit", "vanilla", "watermelon", "xylocarp", "yellow watermelon", "zucchini"];
    var wordToGuess = words[Math.floor(Math.random() * words.length)];
    var incorrectGuesses = [];
    var gameStatus = "";
    var guessInput = document.getElementById("guess-input");
    var wordToGuessDisplay = document.getElementById("word-to-guess");
    var incorrectGuessesDisplay = document.getElementById("incorrect-guesses");
    var gameStatusDisplay = document.getElementById("game-status");

    // Initialize the word to guess display
    var wordToGuessArray = [];
    for (var i = 0; i < wordToGuess.length; i++) {
        wordToGuessArray.push("_");
    }
    wordToGuessDisplay.innerHTML = wordToGuessArray.join(" ");

    // Function to handle a guess
    function guessLetter() {
        var guess = guessInput.value.toLowerCase();
        if (guess.length === 1 && guess.match(/[a-z]/i)) {
            if (wordToGuess.includes(guess)) {
                for (var i = 0; i < wordToGuess.length; i++) {
                    if (wordToGuess[i] === guess) {
                        wordToGuessArray[i] = guess;
                    }
                }
                wordToGuessDisplay.innerHTML = wordToGuessArray.join(" ");
            } else {
                incorrectGuesses.push(guess);
                incorrectGuessesDisplay.innerHTML = incorrectGuesses.join(" ");
            }
            guessInput.value = "";
        }
        if (wordToGuessArray.indexOf("_") === -1) {
            gameStatus = "You win!";
        } else if (incorrectGuesses.length === 6) {
            gameStatus = "You lose!";
        }
        gameStatusDisplay.innerHTML = gameStatus;
    }
</script>