Learn to Code JavaScript!

Brought to you by Galvanize. Learn more about the way we teach code at galvanize.com.

Overview

In this course, we'll be going over the following!

Basic syntax of JavaScript
Variables and Functions
Conditional statements (if, else if, else)
Build a “Rock, Paper, Scissors” application

While not required, reviewing our HTML & CSS course can help!

Setting Up Your Computer

For this workshop, you need to have the following:

Install a text editor! We recommend Atom.io
Have an updated web browser! We recommend Google Chrome

What IS JavaScript?

Making its first appearance in 1995, JavaScript was created by an engineer at Netscape to provide a user-friendly, lightweight programming language that can be easily adapted for the rise of the Internet. Now, with HTML and CSS, it is one of the core languages of the Internet and is growing quickly to accommodate beyond the client-side.

JavaScript allows web pages to do more than just “sit there." You can animate, calculate, etc. - you can do it all! It is a great programming bridge between “design” and “development” that allows for endless creativity.

Common confusion: JavaScript is NOT Java. They are largely different programming languages and should not be confused with one another.

A Quick Mini-Tutorial

In order to go over some basic JavaScript concepts, let's follow a tutorial provided by the JavaScript.com team.

It's only 8 lessons and takes less than 5 minutes.

https://www.javascript.com/try

Dive a Little Deeper

Let's review some of the basic syntax of JavaScript.

var - defines a variable (an object of some value)
; - terminator, commonly found at the end of a code operation
"word" - quotes create strings, which are a form of data
function() - performs some action or method
{} - block notation, contains code that can be initialized by a function
. - dot notation, allows for the chaining of variables and functions

JavaScript is an Object-Oriented Language, a common paradigm of coding that occurs in many other languages and can help you learn them as well.

Variables

Variables are essentially containers for storing data, values, etc. In JavaScript, you must declare them with var first, then define them with =.

Syntax:

var price1 = 5;
var price2 = 6;
var total = price1 + price2;

What is the value of total?

Variables can store a variety of data types:

Strings - “Hello, my name is Lee.”
Numbers - 40, 0.15
Boolean - True or False
Null - literally nothing
“” - undefined value
Functions - here we go…!

Gut check!

What's the difference between =,==, and ===? I see this all the time.

#####= is known as the assignment operator It sets variables equal to a specific value.

var foo = 1

`==` is known as the abstract equality comparison

It compares two items to see if they are of equal value, but it ignores if they are the same exact type of data.

“1” == 1 => True
Null == undefined => True

`===` is known as the strict equality comparison

It compares the value & type of the items to see if they are exactly the same. In the case of null vs undefined, null is more specifically typed than undefined, so they are not exactly the same value.

“1” === 1 => False
Null === undefined => False

Functions

Functions are blocks of code that perform tasks for us.

In JavaScript, you follow the general syntax: 1) declare, 2) define, 3) call (invoke).

Syntax:

var multiply = function(a,b){
return a * b
};
multiply(2,4);

~What is the value produced by this function?

Conditional Statements

Remember Choose Your Own Adventure books?

Conditional statements work a lot like them and follow the basic format: if, else, else if...

If Statements

if - if what’s in the parameters is True, then a block of code will run. If it’s False, the code will not run.

if (hour < 18) {
	greeting = "Good day";
}

if statements by themselves default to True.

Else Statements

else - what if you wanted the code to do something else besides nothing if it’s False?

if (hour < 18) {
	greeting = "Good day";
} else 
	{ greeting = “Go away.”;
}

Else if Statements

else if - What if another scenario comes up?

Add an else if in between the if and else statements.

if (hour < 18) 
{greeting = "Good day";} 
else if (hour < 9) 
{greeting = “OK day”;}
else {greeting = “Go away.”;}

This code is actually broken. Can you figure out why?

Recap of Conditional Rules

If statements perform an action if the statement is True
Else statements perform an action if the statement is False
Else if statements perform an action if the first is False but the second is True Is there any other way to do this?

LET'S CODE

Time for us to make our Rock, Paper, Scissors application!

Go to: https://github.com/GalvanizeOpenSource/Learn-To-Code-JavaScript/
Download the zip file of our code
Open the files in your text editor 4. index.html 5. CSS/style.css
Open the index.html file in your web browser

4 Steps To Building This App

Get the user's choice
Get the computer's choice
Teach the computer how to guess rock, paper, or scissors
Compare their choices and tell the user the result

1. Get the user's choice

Assign a prompt method to the variable userChoice: The prompt method gets input from the user, prompt has an optional message parameter which you can use to ask the user for a response.

var userChoice = prompt("Do you choose rock, paper or scissors?");

This line creates a variable called userChoice to represent the users response.

Question: Why is this a terrible way to get user input?

2. Get the computer's choice

Assign a Math.random() method to the variable computerChoice:

What is Math in JavaScript?

Math.random() returns a random floating point number between 0 and 1.

var computerChoice = Math.random();

Here we are setting a variable named computerChoice to the result of Math.random().

Question: How else can we get a random choice?

3. Teach the computer rock, paper, scissors.

This is our first conditional statement.

We change the value of computerChoice to either rock, paper, or scissors depending on what number the computerChoice variable gets set to when we run the program.

Computers don't speak English (well, not exactly), so we need to speak in a language they understand: numbers.

if (computerChoice <= 0.33) {
    computerChoice = "rock";
} else if (computerChoice <= 0.66) {
    computerChoice = "paper";
} else {
    computerChoice = "scissors";
}

At this point the computer is ready to rumble with it's choice, and the user has made theirs.

IT'S GO TIME!!! (Not so fast, bub.) First we need to tell the computer how to decide who wins. In order to do that, we're going to need to create a function!

4. Compare the choices and tell the user of the result.

Here we're creating a function called compare. The compare function takes two arguments choice1 and choice2.

var compare = function(userChoice, computerChoice) {
    if (userChoice  === computerChoice) {
        window.alert("The result is a tie!");
    } else if(userChoice === "rock") {
        if (computerChoice === "scissors") {
            window.alert("Rock wins!");
        } else {
            window.alert("Paper wins");
        }
    } else if(userChoice === "paper") {
        if(computerChoice === "rock") {
            window.alert("paper wins!");
        } else {
            window.alert("scissors wins!");
        }
    } else if(userChoice === "scissors") {
        if (computerChoice === "rock") {
            window.alert("Rock wins");
        } else {
            window.alert("scissors wins");
        }
    }
};

4.5 Calling the compare function

We're passing values of userChoice and computerChoice to run the equation.

The function is called when someone clicks the button via the onclick attribute!

<button class="button" onclick="compare(userChoice, computerChoice);">LETS PLAY RPS!</button>

Play around in the sandbox some more!

"I want to play the game again. Make a button I can press to play again!"
"When I win, I want the game to congratulate me by my name!"
"I don't ever want to lose. Make it so I always win."
"I want the JavaScript code to work on other HTML files. How do I do this?"

YOU DID IT, YOU'RE NOW A JAVASCRIPT CODER!

Want to learn more? Visit one of our nearby Learn to Code sessions or check out our other tutorials:

You can also check out our evening courses at galvanize.com/workshops:

Zero to Web Designer in 8 Weeks
Foundations in JavaScript in 8 Weeks

If you're ready for a full-fledged immersive program, Galvanize offers the following:

Galvanize Full Stack Immersive Program

24 Week Full-Time Program
97% Job Placement Rate within six months
Average starting salary: $77,000 per annum
Scholarships available for those who qualify

To learn more, email our enrollment department at enrollment@galvanize.com.

About the Authors

Graham McBain is an alum of the 3rd cohort of the Galvanzie Web Development Program. He previously served as Evangelist for Galvanize based in the Colorado area. Graham believes that programming is more accessible than people think and is passionate about showing people the path to becoming a developer.

Lee Ngo is an evangelist for Galvanize based in Seattle. Previously he worked for UP Global (now Techstars) and founded his own ed-tech company in Pittsburgh, PA. Lee believes in learning by doing, engaging and sharing, and he teaches code through a combination of visual communication, teamwork, and project-oriented learning.

You can email him at lee.ngo@galvanize.com for any further questions.

GalvanizeOpenSource/Learn-To-Code-JavaScript