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<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no">
<title>JavaScript First Steps</title>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/reveal.js/4.3.1/reset.min.css" integrity="sha512-Mjxkx+r7O/OLQeKeIBCQ2yspG1P5muhAtv/J+p2/aPnSenciZWm5Wlnt+NOUNA4SHbnBIE/R2ic0ZBiCXdQNUg==" crossorigin="anonymous" referrerpolicy="no-referrer" />
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<style>
.reveal code {
color: var(--r-link-color-hover);
}
</style>
</head>
<body>
<div class="reveal">
<div class="slides">
<section data-markdown>
<textarea data-template>
## JavaScript First Steps
### A [FrontendMasters](https://frontendmasters.com) course by [AnjanaVakil](https://twitter.com/AnjanaVakil)
[anjana.dev/javascript-first-steps](https://anjana.dev/javascript-first-steps)
</textarea>
</section>
<section data-markdown data-separator-vertical="\n--\n">
<textarea data-template>
### About this course
- Taking our *first steps* in an infinite journey
- Hands-on projects
- Just-in-time vs. just-in-case learning
--
### Grand plan
<span style="color:var(--r-background-color);">time</span> | Part 1 | Part 2 | Part 3
--- | --- | --- | ---
topics | DOM <br> datatypes <br> arrays & objects | functions <br> events <br> branches & loops | (a)sync <br> pro syntax <br> bugs & errors
project | tic tac toe | quiz game | doggos
--
### Ground rules
- Everyone belongs here!
- There are no "dumb" questions
- Growth > Goalposts
</textarea>
</section>
<section data-markdown data-separator-vertical="\n--\n" >
<textarea data-template>
# Part 1
--
### Goals
- Get hands-on with JS
- Explore & modify a web page
- Meet common data types & operators
- Declare variables to remember values
- Collect values into objects & arrays
- Play a Tic-Tac-Toe game in the browser!
--
### Ready?
# Let's go!
</textarea>
</section>
<section data-markdown data-separator-vertical="\n--\n">
<textarea data-template>
## JavaScript!
### What? Why? How?
--
### What is JS?
--
```js
let js = {
name: "JavaScript",
abbreviation: "JS",
isAwesome: true,
officialSpec: "ECMAScript",
birthYear: 1995,
creator: "Brendan Eich"
};
if (js.isAwesome) {
shout("hell yes JS!");
}
```
--
### Why do we need JS?
--
## HTML & CSS & JS: BFFs!
--
<img src="https://media4.giphy.com/media/3o6gE8sp8lYiUBgx8Y/giphy.gif?cid=ecf05e47qgttnhw10sv7okbd6osgrjh1kb2pubtrdazuwtoi&rid=giphy.gif&ct=g" alt="Hamilton GIF by Tony Awards via Giphy" width=700 />
--
### How do we write JS?
--
<img src="https://media1.tenor.com/images/bbb7a06768e4f3c507632383b73eb9a1/tenor.gif?itemid=9213220" alt="Gif of girls performing 'light as a feather, stiff as a board' ritual in 'The Craft'" />
--
<img src="http://1.bp.blogspot.com/-mULfDILNkLQ/Uecl0_H_6hI/AAAAAAAAJiI/vR4dwnwrphs/s1600/the-craft-the-craft-20560404-1842-1219.jpg" alt="Still of girls performing summoning ritual in a circle of candles on the beach, from 'The Craft'" />
--
### ~~How~~ *Where* do we write JS?
--
- **The browser's JS `console`**
- Local text file in editor, e.g. TextEdit, [VS Code](https://code.visualstudio.com/)
- Online playground e.g. [CodePen](https://codepen.io), [CodeSandbox](https://codesandbox.io)
--
## Let's do it!
1. Open [1-tictactoe.html](./1-tictactoe.html) in your browser<br>(`File` > `Open file...`)
1. Inspect the page to open DevTools<br>(Right click > `Inspect`)
1. Click on `Console` tab
</textarea>
</section>
<section data-markdown data-separator-vertical="\n--\n" data-auto-animate>
<textarea data-template>
## The DOM
### Document Object Model
--
### A simple `document`
```html [ 2-8 | 3 | 4-7 | 5-6]
<!DOCTYPE html>
<html lang="en-US">
<head>...</head>
<body>
<header>...</header>
<div id="board">...</div>
</body>
</html>
```
Let's draw the DOM tree!
--
### Reading the DOM with JS
Let's dig into this `document`!
--
```js
document
```
<p class="fragment">the entire HTML document</p>
--
```js
document.title
```
<p class="fragment">the page (document) title</p>
--
```js
document.body
```
<p class="fragment">the <code>body</code> element</p>
--
```js
document.body.children
```
<p class="fragment">all the elements within the <code>body</code></p>
--
```js
document.getElementById("board")
```
<div class="fragment" data-fragment-index="2"><pre class="js hljs"><code>document.querySelector("#board")</code></pre></div>
<p class="fragment" data-fragment-index="1">the (first) element with <code>id="board"</code></p>
--
```js
document.getElementsByTagName("h1")
```
<div class="fragment" data-fragment-index="2"><pre class="js hljs"> <code>document.querySelectorAll("h1")</code></pre></div>
<p class="fragment" data-fragment-index="1">all the <code>h1</code> elements</p>
--
```js
document.getElementsByClassName("player")
```
<div class="fragment" data-fragment-index="2"><pre class="js hljs"><code>document.querySelectorAll(".player")</code></pre></div>
<p class="fragment" data-fragment-index="1">all the elements with <code>class="player"</code> </p>
--
<pre class="r-fit-text js hljs"><code>document.getElementsByClassName("player").length</code></pre>
<pre class="r-fit-text js hljs"> <code>document.querySelectorAll(".player").length</code></pre>
<p class="fragment" >the number of elements with <code>class="player"</code> </p>
--
<pre class="r-fit-text js hljs"><code>document.getElementById("p1-name").textContent</code></pre>
<p class="fragment">the text inside the element with <code>id="p1-name"</code></p>
--
### *Do you expect me to remember all this!?!??!*
<img src="https://gifimage.net/wp-content/uploads/2017/08/overwhelmed-gif-6.gif" alt="Gif of Steve Urkel looking overwhelmed" />
--
The three most important letters in web development:
# ✨MDN✨
[developer.mozilla.org](https://developer.mozilla.org)
--
## Exercise
Type commands in the console to retrieve:
1. all the `p` elements
1. the text "X"
1. the number of squares in the board
1. the text "A game you know"
--
### Editing the DOM with JS
--
```js
document.title = "My Page"
```
<p class="fragment">change the page title</p>
<p class="fragment" style="font-style:italic;">note the double-quotes</p>
--
<pre class="r-fit-text js hljs"><code>document.getElementById("p1-name").textContent = "Sofia"</code></pre>
<p class="fragment">replace the text of the <code>#p1-name</code> element</p>
--
<pre class="r-fit-text js hljs"><code>document.getElementById("p1-name").append(" & friends")</code></pre>
<p class="fragment">add to the end of the element's current text</p>
--
## Exercise
1. Change the player names to you & neighbor
1. Swap the player symbols
1. Change subtitle to "A game you know and love"
</textarea>
</section>
<section data-markdown data-separator-vertical="\n--\n">
<textarea data-template>
## Values & Data Types
--
### What are these?
`"Tic Tac Toe"`
`9`
`"#board"`
--
# Values
<p class="fragment">chunks of information we want to work with</p>
<p class="fragment">that information (data) can be of different types</p>
--
## text data
e.g. `"Tic Tac Toe"` or `"#board"`
<p class="fragment">aka...</p>
--
## strings
<img src="https://i0.wp.com/www.muffinchanel.com/wp-content/uploads/2020/09/muffinchanel-bracelet-inspiration-pura-vida-inspired-alphabet-bead-bracelets-wax-string-letter-friendship-bracelets-with-seed-beads-4.png?resize=768%2C756&ssl=1" alt="Image of beaded bracelets with letter beads spelling out '❤️', 'LOVE', 'CE❤️', 'ILYSM', 'SASHA', 'BLM', 'HELLO❤️', '❤️PIZZA'" width=500 />
--
All of these are strings:
- `"Hello!"`
- `'I like single-quotes'`
- <code>\`I ❤️ backticks\`</code>
- `'867-5309'`
- `"42"`
--
## `"42"` vs. `42`
*are these the same thing?*
--
## `typeof`
tells you the type of a value
--
Try it!
```js
typeof "42"
```
```js
typeof 42
```
--
## numbers
<img src="https://media3.giphy.com/media/OxeCmRsZsXSCI/giphy.gif?cid=790b7611df6245385829b15db4d7ebd2948ea669e07b5fbb&rid=giphy.gif&ct=g" alt="Gif of Count von Count and the Sesame Street muppets dancing and presenting the number 2" />
--
All of these are numbers:
- `9`
- `525600`
- `-3.45`
- `1.21e9`
- `Infinity`
--
### JS has two kinds of data:
- Primitive types (e.g. strings, numbers)
- Objects (e.g. `document` & friends)
--
## Primitive data types
- `string`
- `number`
- `boolean`
- `undefined`
- `null`
- A couple [others](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#primitive_values) we don't need yet
--
## booleans
<div style="display:flex">
<img src="https://media0.giphy.com/media/dXFKDUolyLLi8gq6Cl/giphy.gif?cid=790b7611e65175eaf20e344bed912deb1bbe1510918127b6&rid=giphy.gif&ct=g" />
<img src="https://media3.giphy.com/media/98maV70oAqIZtEYqB4/giphy.gif?cid=790b76119164770fd461651da0b494e09dd0e62870f30c3a&rid=giphy.gif&ct=g" />
</div>
--
## `undefined` & `null`
<img src="https://media4.giphy.com/media/RkN1YEwSP4GBvv5bDC/giphy.gif?cid=790b7611f7bab2fa354705ec00978abc19a34b9b64e56d94&rid=giphy.gif&ct=g" alt="Gif of woman gesturing and saying 'blank void of nothingness', from Now Apocalypse on Starz"/>
--
<div style="display:flex;">
<div style="display:flex; flex-direction:column;">
<code>undefined</code>
<img height=250 src="http://campusriot.com/wp-content/uploads/2013/06/I-Want-It-That-Way-Backstreet-Boys-Gif.gif" alt="Gif of Backstreet Boys singing 'Tell my why, Ain't nothin but a mistake...'" />
accidental nothing
</div>
<div style="display:flex; flex-direction:column;">
<code>null</code>
<img height=250 src="https://c.tenor.com/AzSrhbW1nYcAAAAC/tenor.gif" alt="Gif of Backstreet Boys singing 'I want it that way'" />
deliberate nothing
</div>
</div>
--
### Exercise
Which data type is each of these values?
- `false`
- `"true"`
- `document.title`
- `"some string".length`
- `null`
(guess first, then use `typeof` to check!)
</textarea>
</section>
<section data-markdown data-separator-vertical="\n--\n">
<textarea data-template>
## Working with Strings
<img width=500 src="https://i0.wp.com/www.muffinchanel.com/wp-content/uploads/2020/09/how-to-make-letter-bead-word-alphabet-bead-bracelets-inspired-by-pura-vida-bracelets-muffinchanel-diy-step-by-step-10.png?w=632&ssl=1" alt="Image of unfinished beaded bracelet spelling 'ALOHA' with text 'Step 13' in corner, via MuffinChanel " />
--
What are strings made of?
<h4 class="fragment">characters</h4>
--
How many characters are in this string?
<pre class="js">
<code>"supercalifragilisticexpialidocious".length</code>
</pre>
```js
"super".length
```
--
Characters are in a specific order
Each gets a number, starting at `0`
<img width=700 height=190 style="object-fit: cover; object-position: 0 -510px;" src="https://i0.wp.com/www.muffinchanel.com/wp-content/uploads/2020/09/how-to-make-letter-bead-word-alphabet-bead-bracelets-inspired-by-pura-vida-bracelets-muffinchanel-diy-step-by-step-7.png?w=631&ssl=1" />
<p class="fragment">aka an "index"</p>
--
What's the first character in the string?
```js
"ALOHA"[0]
```
--
What's the third character in the string?
```js
"ALOHA"[2]
```
--
What's the index of a specific character?
<pre class="fragment"><code>"ALOHA".indexOf("L")</code></pre>
<pre class="fragment"><code>"ALOHA".indexOf("A")</code></pre>
<pre class="fragment"><code>"ALOHA".indexOf("Q")</code></pre>
--
Does this string contain some other string?
<pre class="fragment"><code>"ALOHA".includes("HA")</code></pre>
<pre class="fragment"><code>"ALOHA".includes("LOL")</code></pre>
--
Does this string start with some other string?
<pre class="fragment"><code>"ALOHA".startsWith("AL")</code></pre>
<pre class="fragment"><code>"ALOHA".startsWith("HA")</code></pre>
--
At what index does this substring begin?
<pre class="fragment"><code>"ALOHA".indexOf("HA")</code></pre>
<pre class="fragment"><code>"ALOHA".indexOf("LOL")</code></pre>
--
Connecting strings together
```js
"ALOHA" + "!"
```
--
<div style="display:flex;">
<img src="https://media0.giphy.com/media/3ohhwr2FHK5u2TZFcI/giphy.gif?cid=790b7611b3d751c8682486f8a5140f1fa2d7c44ba387cfb7&rid=giphy.gif&ct=g" alt="Gif from Schitt's Creek of Alexis looking offended asking 'Why are you yelling at me?!'" />
<img src="https://media2.giphy.com/media/UtuJHoRbWW2eb9K8LQ/giphy.gif?cid=ecf05e47hmqd6amklrxj0i3nfbpqlwwpvy7smtfmkqvtzcjw&rid=giphy.gif&ct=g" alt="Gif from Schitt's Creek of Moira looking offended saying 'There's no need to raise your voice'" />
</div>
```js
"ALOHA".toLowerCase()
```
--
### Exercise
Use our new string superpowers to:
- Add your last name in the players listing
- Retrieve the first "T" in the page title
- Answer whether the page title contains the string "JavaScript"
- Capitalize the heading "Tic Tac Toe"
--
There is a lot more we can do with strings...
<img src="https://media2.giphy.com/media/THrVdFFbwhwxNPxfGi/giphy.gif?cid=ecf05e47hxna43czb0oedyxy295x2ywq34xdo4yjvydqhqcr&rid=giphy.gif&ct=g" alt="Gif of Michaela Coel saying 'Sometimes it gets a bit much'" />
--
Remember ✨MDN✨ is your friend!
[JavaScript > Standard built-in objects > String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)
</textarea>
</section>
<section data-markdown data-separator-vertical="\n--\n">
<textarea data-template>
## Operators
<img src="https://media4.giphy.com/media/YX6YQZfuRN0nC/giphy.gif?cid=ecf05e47qz4szu7ek9s2zbxa7i4e86beyggj5nwytiq27pr4&rid=giphy.gif&ct=g" alt="Gif of Sade singing 'Smooth'" />
--
We've already seen a couple of operators:
- `"ALOHA" + "!"`
- `typeof "value"`
--
`+` is an operator with several different uses:
<ul>
<li class="fragment">What does it do when operating on strings?</li>
<li class="fragment">Any guess what else it can operate on? </li>
<li class="fragment">How many values does it operate on at a time?</li>
</ul>
--
### Arithmetic operators
- `+` add
- `-` subtract
- `*` multiply
- `/` divide
--
### Order of operations
`4 + 1 * 2 * 4 + 2`
same as in math, use `()` to group
`((4 + 1) * 2 * 4) + 2`
--
## Exercise
Use arithmetic operators to compute:
- The total number of siblings of your parents
- The average number of hours you slept this week
- The number of dogs you'd pet in a week if you pet 1 dog per hour while awake
--
### Comparison operators
- `>` greater than
- `<` less than
- `>=` greater than or equal to
- `<=` less than or equal to
--
`5 > 4`
What type of value will this return?
--
### Equality operators
strict | loosey-<br>goosey | meaning
--- | --- | ---
`===` | `==` | equals
`!==` | `!=` | does not equal
--
Do these differ? How?
strict | vs. | loosey-goosey
--- | --- | ---
`1 === 1` | vs. | `1 == 1`
`"1" === "1"` | vs. | `"1" == "1"`
`1 === "1"` | vs. | `1 == "1"`
<p class="fragment">You should almost always use the <b>strict</b> version</p>
--
### JS has lots of operators!
<p class="fragment">Any guesses what else is out there?</p>
<p class="fragment">Where can you find them all?</p>
--
✨MDN✨
[JavaScript > Expressions & Operators](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators)
</textarea>
</section>
<section data-markdown data-separator-vertical="\n--\n">
<textarea data-template>
## Expressions
<img src="https://media.tenor.com/images/6bbe631a75e9da8d1c316bf89ed460cc/tenor.gif" alt="Gif of Madonna dancing & singing 'Express Yourself'" />
--
Are these values?
- `4 / 2 * 10`
- `"Frontend" + "Masters"`
- `5 > 4 !== 3 > 4`
--
an expression *evaluates* (aka *resolves*) to a value
--
<img src="https://occ-0-1722-1723.1.nflxso.net/dnm/api/v6/X194eJsgWBDE2aQbaNdmCXGUP-Y/AAAABVQNgd4IpL64y3okatJlrMQUv0RmPmsyFalQ2aNV5G8SLFI4ghuVYMTV-VTLbHA2G9HQ7Gv1x5RIF7zhGf4Ion3IKDP8.jpg?r=4d2" alt="Image from film 'New York Minute' with Mary Kate and Ashley Olsen looking at each other seated in a cab, with title overlay" />
--
✨MDN✨
[JavaScript > JS Guide > Expressions & Operators](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Expressions_and_Operators)
</textarea>
</section>
<section data-markdown data-separator-vertical="\n--\n">
<textarea data-template>
## Variables
<img src="https://www.surlyhorns.com/board/uploads/monthly_2020_08/iu-2.gif.dff1f3975b6ad925cbb783079c18422b.gif" alt="Gif of Sarah McLachlan singing 'I will remember you'" />
--
Variables let us **remember** values
```js
let remember = "Sept. 21";
```
What do you notice about the line of code above?
--
### Declaring a variable
<img src="https://memeguy.com/photos/images/mrw-i-open-my-credit-card-statement-109160.gif" alt="Gif from 'The Office' of Michael Scott yelling 'I declare... bankruptcy!'" />
```js
let bankruptcy;
```
What do you think is the value of `bankruptcy`?
--
### Assigning a variable
```js
let myDeclaredVariable;
myDeclaredVariable = "so value, much wow";
```
--
### Declaring & assigning at once
```js
let myAssignedVariable = "such efficient, amaze";
```
--
### Declaring & assigning forever
`const` declares & assigns a "constant"
aka a variable that can't be changed
```js
const myUnchangeableVariable = "Never gonna give you up";
```
*we'll talk more about this later*
--
### Using a variable
`answerToLife - 10`
`myDeclaredVariable.toUpperCase()`
--
### Variable names
- `validVariable`
- `also_valid_but_less_common`
- `Oddbut_Technicallyfine2`
- ~`0chanceThisWillWork!`~
--
<img src="https://upload.wikimedia.org/wikipedia/commons/thumb/c/c8/CamelCase_new.svg/640px-CamelCase_new.svg.png" alt="Illustration of a camel with the word 'camelCase' positioned so that the captial C is the camel's hump" />
--
## Exercise
Declare & assign variables to remember:
- Your name
- The combined age of your parents
- The `#board` element on the page
--
What really **are** variables though??
--
variables *contain* values?
--
variables ~contain~ *point to* values
--
<img src="https://media2.giphy.com/media/3orieSlpoJxbN34HBK/giphy.gif?cid=790b76110319b1d53fe86c88f59f9ebc32b250b97736c438&rid=giphy.gif&ct=g" alt="Gif from the Simpsons of someone pressing the speed dial button on a phone, captioned '(Dialing)'" />
--
<img src="https://www.akruto.com/images/how-to-save-and-share-iphone-contacts/add-to-contacts-large.png" alt="Screenshot of an iPhone messaging the number '555-555-5555' with the options to 'Call (555) 555-5555', 'FaceTime Audio', 'Send Message', 'Add to Contacts' highlighted in a red box, 'Copy', 'Cancel'" />
--
What happens when this code runs?
```js
let answerToLife = ((4 + 1) * 2 * 4) + 2;
```
--
What happens when this code runs?
```js
let scrub = "guy that thinks he's fly";
let busta = scrub;
scrub = "guy that can't get no love from me";
```
</textarea>
</section>
<section data-markdown data-separator-vertical="\n--\n">
<textarea data-template>
## Statements vs. Expressions
<img src="https://media4.giphy.com/media/55GrSbPv8p4pp5E3vC/giphy.gif?cid=790b7611f3e548491596af24d8df5e50a8b3f5baca55fb77&rid=giphy.gif&ct=g" alt="Gif from HBO's 'Euphoria' of Colman Domingo saying 'I can't tell if that's a statement or a question'" />
--
An expression "asks" JS for a value
```
myAssignedVariable
6 + 4
document.getElementById("board")
```
--
A statement "tells" JS to do something
(e.g. declare/assign a variable)
```
let ten = 6 + 4;
myDeclaredVariable = "new value";
let board = document.getElementById("board");
```
--
<p class="r-fit-text">We'll see more kinds of statements later in the course</p>
```js
function add(x, y) {
return x + y;
}
let biggest;
if (5 > 4) {
biggest = 5;
} else {
biggest = 4;
}
for (let character of "string") {
console.log(character);
}
```
</textarea>
</section>
<section data-markdown data-separator-vertical="\n--\n">
<textarea data-template>
## Arrays
<img src="https://media1.giphy.com/media/KMCapxEUpxTMxhnarh/giphy.gif?cid=ecf05e47gqpnohggvkpijhvkurlz3dkeuxvr28gmxvff0es1&rid=giphy.gif&ct=g" alt="Gif from 'Star Trek Discovery' of Michelle Yeoh saying 'You deserve... many things'" />
--
Arrays let us keep multiple values together in a single collection
```js
let synonyms = ["plethora", "array", "cornucopia"];
```
<img src="https://media1.giphy.com/media/QfGYYVrbay6kssMrYn/giphy.gif?cid=790b7611dba71cb23b707b58277a0e27b04c0f48f848072c&rid=giphy.gif&ct=g" alt="Gif of Quinta Brunson gesturing and saying 'Plethora, Array, Cornucopia'" />
--
Like strings, arrays have a `length`
```js
synonyms.length
```
And each value has an index
```js
synonyms[1]
synonyms.indexOf("cornucopia")
```
--
Also like strings, we can check if an array contains a certain value
```js
synonyms.includes("plethora")
synonyms.includes("variety")
```
--
Unlike strings, we can modify arrays
```js
synonyms[1] = "variety";
let lastItem = synonyms.pop();
synonyms.push("multitude");
```
What does each of these lines do? Try it out!