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<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Class 2 - Intro to JavaScript - Girl Develop It</title>
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</head>
<body>
<div class="reveal">
<div class="slides">
<section>
<img src="img/circle-gdi-logo.png" alt="BDI Logo" class="noborder" style="max-height:400px;">
<h1>Introduction to JavaScript</h1>
<h2>Class 2</h2>
</section>
<!-- Review -->
<section>
<h3>Let's Look Back</h3>
<img src="img/backwards-dance.jpg" alt="Woman looking backward as she dances"/>
<p class="credit">Photo credit: <a href="http://www.flickr.com/photos/zeepack/4398082292/" target="_blank">Deepak Bhatia</a> <a href="http://creativecommons.org/licenses/by-nc/2.0/" target="_blank">cc</a></p>
</section>
<section>
<h3>Code Search</h3>
<p>In this code, spot the comment, variables, and operators.</p>
<pre><code class="javascript">var billPreTip = 10;
var tipPercent = 0.15; // Can be changed
var billTip = billPreTip * tipPercent;
var receipt = 'Meal: ' + billPreTip + ' Tip: ' + billTip +
' Total: ' + (billPreTip + billTip);
console.log(receipt);
</code></pre>
</section>
<!-- Functions -->
<section>
<h3>Functions</h3>
<p>Functions are separable, reusable pieces of code.
<img src="img/legos.jpg" alt="Pile of legos"/>
<p class="credit">Photo credit: <a href="http://www.flickr.com/photos/catzrule/9940388305/">Rick Payette</a> <a href="http://creativecommons.org/licenses/by-nc-sa/2.0/">cc</a>
</section>
<section>
<h3>Declaring Functions</h3>
<p>To declare (create) a function, you can give it a name, then include all the code for the function inside curly brackets <code>{}</code></p>
<pre><code class="javascript">function parrotFacts() {
console.log('Some parrot species can live for over 80 years');
console.log('Kakapos are a critically endangered flightless parrot');
}
</code></pre>
<p>Functions can have multiple lines.</p>
</section>
<section>
<h3>Using Functions</h3>
<p>To invoke (use) a function, you type its name, followed by parenthesis <code>()</code></p>
<pre><code class="javascript"> parrotFacts();</code></pre>
<p>We'll talk about what can go inside those parenthesis in a minute! For now, leave them empty.</p>
</section>
<section>
<h3>What's going on here?</h3>
<p>A function is a group of code you can reuse many times. Whenever you invoke a function by using it's name, you tell the browser to run the code inside the function.</p>
<p>You must declare a function before you can use it.</p>
</section>
<section>
<h3>Let's Develop It</h3>
<p>Write a function that outputs a sentence. Then invoke that function later in your code.</p>
</section>
<section>
<h3>Arguments</h3>
<p>Functions can accept input values, called <code>arguments</code>.</p>
<pre><code class="javascript">function callKitten(kittenName){
console.log('Come here, ' + kittenName + '!');
}
callKitten('Fluffy'); // outputs 'Come here, Fluffy!'
function addNumbers(a, b){
console.log(a + b);
}
addNumbers(5, 7); // outputs 12
addNumbers(9, 12); // outputs 21
</code></pre>
</section>
<section>
<h3>Arguments</h3>
<p>You can also pass <code>variables</code> into functions. These variables do not need to have the same name as the function arguments.</p>
<pre><code class="javascript">function addOne(num){
var newNumber = num + 1;
console.log('You now have ' + newNumber);
}
// Declare variables
var numberOfKittens = 5;
var numberOfPuppies = 4;
// Use them in functions
addOne(numberOfKittens);
addOne(numberOfPuppies);
</code></pre>
</section>
<section>
<h3>Let's Develop It</h3>
<p>Write a simple program to combine a first name and a last name inside a function. Then update the function to accept a first and last name as arguments.</p>
</section>
<!-- returning values -->
<section>
<h3>Returning Values</h3>
<p>You can have a function give you back a value, to use later.</p>
<pre><code class="javascript">function square(num) {
return num * num;
}
console.log(square(4)); // outputs '16'
var squareOfFive = square(5); // squareOfFive equals '25'
</code></pre>
<p><code>return</code> will immediately end a function.</p>
</section>
<section>
<h3>Let's Develop It</h3>
<p>Add a return statement to your 'name' function. Use that function to set the value of a variable.</p>
</section>
<!-- Variable Scope -->
<section>
<h3>Variable Scope</h3>
<p>The scope of a variable determines where it's value is accessible throughout your program.</p>
<img src="img/footprints.jpg" alt="Footprints being washed away"/>
<p class="credit">Photo credit: <a href="http://www.flickr.com/photos/heyvikram/187950111/" target="_blank">_vikram</a> <a href="http://creativecommons.org/licenses/by-nc/2.0/" target="_blank">cc</a></p>
</section>
<section>
<h3>Global Scope</h3>
<p>A variable declared outside of a function has a <code>global scope</code> and can be accessed anywhere, even inside of functions.</p>
<pre><code class="javascript">var awesomeGroup = 'Girl Develop It'; // Global scope
function whatIsAwesome() {
console.log(awesomeGroup + ' is pretty awesome.'); // Will work
}
whatIsAwesome();
</code></pre>
</section>
<section>
<h3>Local Scope</h3>
<p>A variable declared inside a function has a <code>local scope</code> and can only be accessed within that function.</p>
<pre><code class="javascript">function whatIsAwesome() {
var awesomeGroup = 'Girl Develop It'; // Local scope
console.log(awesomeGroup + ' is pretty awesome.'); // Will work
}
whatIsAwesome();
console.log(awesomeGroup + ' is pretty awesome.'); // Won't work
</code></pre>
</section>
<!-- Boolean -->
<section>
<h3>Boolean Variables</h3>
<img src="img/kitten-switch.jpg" alt="Kitten with light switch"/>
<p class="credit">Photo credit: <a href="http://www.flickr.com/photos/elycefeliz/5726163170/" target="_blank">elycefeliz</a> <a href="http://creativecommons.org/licenses/by-nc/2.0/" target="_blank">cc</a></p>
</section>
<section>
<h3>Boolean Variables</h3>
<p>Boolean variables represent the logical values <code>true</code> and <code>false</code></p>
<pre><code class="javascript">var catsAreBest = true;
var dogsRule = false;
</code></pre>
</section>
<section>
<h3>Boolean Variables</h3>
<p>Some values are considered <code><a href="https://developer.mozilla.org/en-US/docs/Glossary/Falsy">falsy</a></code> and will evaluate to <code>false</code> in a Boolean context.</p>
<pre><code class="javascript">// the following variables will evaluate as false
var myName = '';
var numOfKids = 0;
var isMarried; // remember a variable with no value is undefined</code></pre>
<p><code>null</code> and <code>NaN</code> will also evaluate as <code>false</code>.</p>
<p>Everything else evaluates as <code>true</code>.</p>
</section>
<!--If/Then-->
<section>
<h3>Control Flow</h3>
<img src="img/fork-path.jpg" alt="Forked path"/>
<p class="credit">Photo credit: <a href="http://www.flickr.com/photos/dennism2/1504087870/" target="_blank">DennisM2</a> <a href="http://creativecommons.org/licenses/by-nc/2.0/" target="_blank">cc</a></p>
</section>
<section>
<h3>The if statement</h3>
<p>Use <code>if</code> statements to decide which lines of code to execute, based on a condition.</p>
<pre><code class="javascript">if (condition) {
// statements to execute
}
</code></pre>
<pre><code class="javascript">var age = 30;
if (age > 18) {
console.log('You are an adult');
}</code></pre>
</section>
<section>
<h3>Comparison Operators</h3>
<table class="smalltext">
<thead>
<tr>
<th>Example</th>
<th>Name</th>
<th>Result</th>
</tr>
</thead>
<tbody>
<tr>
<td><code>a == b</code></td>
<td>Equal</td>
<td><strong><code>TRUE</code></strong> if <code>a</code> is equal to <code>b</code> (can be different types).</td>
</tr>
<tr>
<td><code>a === b</code></td>
<td>Identical</td>
<td>
<strong><code>TRUE</code></strong> if <code>a</code> is equal to <code>b</code>, and the same type. </td>
</tr>
<tr>
<td><code>a != b</code></td>
<td>Not equal</td>
<td><strong><code>TRUE</code></strong> if <code>a</code> is not equal to <code>b</code> (can be different types).</td>
</tr>
<tr>
<td><code>a !== b</code></td>
<td>Not identical</td>
<td><strong><code>TRUE</code></strong> if <code>a</code> is not equal to <code>b</code>, or they are not the same type.</td>
</tr>
<tr>
<td><code>a < b</code></td>
<td>Less than</td>
<td><strong><code>TRUE</code></strong> if <code>a</code> is strictly less than <code>b</code>.</td>
</tr>
<tr>
<td><code>a > b</code></td>
<td>Greater than</td>
<td><strong><code>TRUE</code></strong> if <code>a</code> is strictly greater than <code>b</code>.</td>
</tr>
<tr>
<td><code>a <= b</code></td>
<td>Less than or equal to </td>
<td><strong><code>TRUE</code></strong> if <code>a</code> is less than or equal to <code>b</code>.</td>
</tr>
<tr>
<td><code>a >= b</code></td>
<td>Greater than or equal to </td>
<td><strong><code>TRUE</code></strong> if <code>a</code> is greater than or equal to <code>b</code>.</td>
</tr>
</tbody>
</table>
</section>
<section>
<h3>Watch out!</h3>
<p>Don't mix up <code>=</code> and <code>==</code> and <code>===</code></p>
<img src="img/caution.jpg" alt="Caution Tape"/>
<p class="credit">Photo credit: <a href="http://www.flickr.com/photos/pictureperfectpose/76138988/" target="_blank">Eugene Zemlyanskiy</a> <a href="http://creativecommons.org/licenses/by-nc/2.0/" target="_blank">cc</a></p>
</section>
<section>
<h3>Let's Develop It</h3>
<p>Make a variable called "temperature". Write some code that tells you to put on a coat if it is below 50 degrees.</p>
</section>
<!--If/else -->
<section>
<h3>Even more control flow</h3>
<img src="img/toomanysigns.jpg" alt="Sign post with multiple signs"/>
<p class="credit">Photo credit: <a href="http://www.flickr.com/photos/thomashawk/2402598275/" target="_blank">Thomas Hawk</a> <a href="http://creativecommons.org/licenses/by-nc/2.0/" target="_blank">cc</a></p>
</section>
<section>
<h3>The if/else statement</h3>
<p>Use <code>else</code> to provide an alternate set of instructions.</p>
<pre><code class="javascript">var age = 30;
if (age >= 16) {
console.log('Yay, you can drive!');
} else {
console.log('Sorry, you have ' + (16 - age) +
' years until you can drive.');
}
</code></pre>
</section>
<section>
<h3>The if/else statement</h3>
<p>If you have multiple conditions, you can use <code>else if</code>.</p>
<pre><code class="javascript">var age = 30;
if (age >= 35) {
console.log('You can vote AND run for President!');
} else if (age >= 30) {
console.log('You can vote AND run for the Senate!');
} else if (age >= 18) {
console.log('You can vote!');
} else {
console.log('You can\'t vote, but you can write your representatives.');
}
</code></pre>
</section>
<section>
<h3>Let's Develop It</h3>
<p>Modify your "wear a coat" code for these conditions:</p>
<ol>
<li>If it's less than 50 degrees, wear a coat.</li>
<li>If it's less than 30 degrees, wear a coat and a hat.</li>
<li>If it's less than 0 degrees, stay inside.</li>
<li>Otherwise, wear whatever you want.</li>
</ol>
</section>
<!-- Logical Operators -->
<section>
<h3>Logical Operators</h3>
<table>
<thead>
<tr>
<th>Example</th>
<th>Name</th>
<th>Result</th>
</tr>
</thead>
<tbody>
<tr>
<td><code>a && b</code></td>
<td>And</td>
<td><strong><code>TRUE</code></strong> if both <code>a</code> and <code>b</code> are <strong><code>TRUE</code></strong>.</td>
</tr>
<tr>
<td><code>a || b</code></td>
<td>Or</td>
<td><strong><code>TRUE</code></strong> if either <code>a</code> or <code>b</code> is <strong><code>TRUE</code></strong>.</td>
</tr>
<tr>
<td><code>!a</code></td>
<td>Not</td>
<td><strong><code>TRUE</code></strong> if <code>a</code> is not <strong><code>TRUE</code></strong>.</td>
</tr>
</tbody>
</table>
</section>
<section>
<h3>Using logical operators</h3>
<p>You can use these operators to combine conditions.</p>
<pre><code class="javascript">var age = 30;
var yearsAsCitizen = 30;
if (age >=30 && yearsAsCitizen > 9) {
console.log('You can run for the Senate!');
} else {
console.log('You are not eligible to run for the Senate');
}</code></pre>
</section>
<section>
<h3>Let's Develop It</h3>
<p>Add a logical operator to your "what to wear" program.</p>
</section>
<!-- Final slides-->
<section>
<h3>You did it!</h3>
<img src="img/kitten-yay.jpg" alt="Happy cat"/>
<p class="credit">Photo credit: <a href="http://www.flickr.com/photos/laura-kali/7399310732/" target="_blank">OnceAndFutureLaura</a> <a href="http://creativecommons.org/licenses/by-sa/2.0/" target="_blank">cc</a></p>
</section>
<section>
<h3>Resources</h3>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide" target="_blank">JavaScript Guide</a>, from the Mozilla Developers Network.</li>
<li><a href="http://www.codecademy.com/tracks/javascript" target="_blank">Code Academy</a>, with interactive JavaScript lessons to help you review.</li>
</ul>
</section>
<section>
<h2>Questions?</h2>
</section>
</div>
<footer>
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Intro to JavaScript -- Girl Develop It --
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