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<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Class 4 - Intro to JavaScript - Girl Develop It</title>
<meta name="description" content="Girl Develop It framework for easily creating beautiful presentations using HTML in GDI theme. Forked from Hakim El Hattab's reveal.js">
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link.type = 'text/css';
link.href = 'css/print/pdf.css';
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<link rel="icon" type="image/x-icon" href="favicon.ico" />
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<body>
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<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 4</h2>
</section>
<!--Intro-->
<section>
<h3>Let's Review</h3>
<img src="img/elephants.jpg" alt="Two elephants interacting"/>
<p class="credit">Photo credit: <a href="http://www.flickr.com/photos/ginable/325235488/" target="_blank">Ginable</a> <a href="http://creativecommons.org/licenses/by-nc-sa/2.0/" target="_blank">cc</a>
</section>
<section>
<h3>Anatomy of a Website</h3>
<p><strong>Your Content</strong><br />
<strong>+ HTML</strong>: Structure<br />
<strong>+ CSS</strong>: Presentation<br />
<strong>= Your Website</strong></p>
<p>A website is a way to present your content to the world, using HTML and CSS to present that content & make it look good.</p>
</section>
<section>
<h3>HTML is Markup</h3>
<img src="img/markup.jpg" alt="Printed document covered in ink marks"/>
<p class="credit">Photo credit: <a href="http://www.flickr.com/photos/nics_events/2349630241/" target="_blank">Nic's events</a> <a href="http://creativecommons.org/licenses/by-nc-sa/2.0/" target="_blank">cc</a>
</section>
<section>
<h3>CSS is Style</h3>
<img src="img/fingernails.jpg" alt="Fingernails with polka-dot paint job"/>
<p class="credit">Photo credit: <a href="http://www.flickr.com/photos/pumpkincat210/4778025555/" target="_blank">pumpkincat210</a> <a href="http://creativecommons.org/licenses/by-nc-sa/2.0/" target="_blank">cc</a>
</section>
<section>
<h3>JavaScript is Interactivity</h3>
<img src="img/confirm_window.jpg" alt="Confirm window in browser"/>
<p class="credit">Photo credit: <a href="http://www.datasprings.com/help/dnn-tutorials/artmid/535/articleid/89/javascript-getting-started-guide" target="_blank">DataSprings</a>
</section>
<section>
<h3>IDs vs Classes</h3>
<p><strong>ID</strong> - Should only apply to one element on a webpage, i.e., you might have an id of <code>banner</code> on your webpage's banner.<br />
The <code>#</code> is how you find ids in CSS.</p><br>
<p><strong>Class</strong> - Lots of elements can have the same class, i.e., There can be many elements with a <code>warning</code> class on one webpage.<br />
The <code>.</code> is how you find classes in CSS.</p>
</section>
<!--The DOM-->
<section>
<h3>Nesting</h3>
<p>HTML elements "nest" inside one another</p>
<img src="img/nesting-dolls.jpg" alt="Russian nesting dolls"/>
<p class="credit">Photo credit: <a href="http://www.flickr.com/photos/johnkay/3539939004/">John K</a> <a href="http://creativecommons.org/licenses/by-nc-sa/2.0/" target="_blank">cc</a>
</section>
<section>
<h3>The DOM Tree: Sample Code</h3>
<p>Oftentimes, people think of HTML as something flat -- a bunch of text with tags in the middle. </p>
<pre><code class="html"><!DOCTYPE html>
<html>
<head>
<title>Test Page</title>
<style>
h1 {
color: red;
}
</style>
</head>
<body>
<h1>My Page</h1>
<p>Hello World!</p>
<img src="http://placekitten.com/g/200/300" alt="cat"/>
</body>
</html>
</code></pre>
</section>
<section>
<h3>The DOM Tree: Sample Model</h3>
<p>However, it is something much more than that. Any HTML document is a tree structure defined by the <strong><a href="https://developer.mozilla.org/en-US/docs/Web/API/Document_Object_Model/Introduction" target="_blank">DOM (Document Object Model)</a></strong>.</p>
<img src="img/dom-tree.png" alt="Simple DOM Tree"/>
</section>
<!--Accessing the DOM-->
<section>
<h3>DOM Access</h3>
<p>Your browser automatically loads the content of a webpage into a <code>Document</code> object which serves as the entry point into a web page's content.</p><br>
<p><strong>Using the <code>document</code> you can:</strong></p>
<ol>
<li>Change the content tree any way you want.</li>
<li>Build an HTML document from scratch.</li>
<li>Access or replace any existing HTML elements in the DOM (also known as existing DOM nodes).</li>
</ol>
</section>
<section>
<h3>Finding Nodes</h3>
<img src="img/search.jpg" alt="A magnifying glass"/>
<p class="credit">Photo credit: <a href="https://flic.kr/p/4UokrH" target="_blank">Jeffery Beall</a> <a href="http://creativecommons.org/licenses/by-nc-sa/2.0/" target="_blank">cc</a>
</section>
<section>
<h3>DOM Access: By Id</h3>
<p>You can find nodes by <code>id</code> using the method:</p>
<pre><code class="javascript">document.getElementById(id);
</code></pre>
<p>For example, to find:</p>
<pre><code class="html"><img id="kittenPic" src="http://placekitten.com/g/200/300" alt="cat"/>
</code></pre>
<p>We would use:</p>
<pre><code class="javascript">var imgKitten = document.getElementById('kittenPic');
</code></pre>
</section>
<section>
<h3>DOM Access: By Tag Name</h3>
<p>You can also get HTML elements by their <code>tag</code> using this method:</p>
<pre><code class="javascript">document.getElementsByTagName(tagName);
</code></pre>
<p>To find:</p>
<pre><code class="html"><ul>
<li>Daisy</li>
<li>Tulip</li>
</ul></code></pre>
<p>We would use:</p>
<pre><code class="javascript">var listItems = document.getElementsByTagName('li');
for (var i = 0; i < listItems.length; i++) {
console.log(listItems[i]);
}
</code></pre>
</section>
<!--
<section>
<h3>Let's Develop It</h3>
<p>Visit <a href="https://google.com" target='_blank'>google.com</a> and practice getting an element by ID and by Tag Name.</p>
</section>
-->
<section>
<h3>DOM Access: HTML 5</h3>
<p>In newer browsers, you can use methods <code><a href="https://developer.mozilla.org/en-US/docs/Web/API/Document/getElementsByClassName" target="_blank">getElementsByClassName</a></code>, <code><a href="https://developer.mozilla.org/en-US/docs/Web/API/Document/querySelector" target="_blank">querySelector</a></code>, and <code><a href="https://developer.mozilla.org/en-US/docs/Web/API/Document/querySelectorAll" target="_blank">querySelectorAll</a></code>.</p><br>
<p>Available in <a href="http://caniuse.com/#search=getElementsByClassName" target="_blank">IE9+, FF3.6+, Chrome 17+, Safari 5+</a>:</p>
<pre><code class="javascript">document.getElementsByClassName(className);
</code></pre><br>
<p>Available in <a href="http://caniuse.com/#search=querySelectorAll" target="_blank">IE8+, FF3.6+, Chrome 17+, Safari 5+</a>:</p>
<pre><code class="javascript">document.querySelector(cssQuery);
document.querySelectorAll(cssQuery);
</code></pre>
</section>
<section>
<h3>getElement vs. getElements</h3>
<p>Any method that starts with <code>getElement</code> will return a <strong>single</strong> node.</p>
<pre><code class="javascript">document.getElementById('uniqueID'); // returns a single node
</code></pre><br>
<p>Any method that starts with <code>getElements</code> will return an <strong>array*</strong> of nodes. To modify a single node, you will need to use bracket notation to get the correct one.</p>
<pre><code class="javascript">document.getElementsByTagName('p'); // returns multiple nodes
var specificParagraph = document.getElementsByTagName('p')[2];
</code></pre>
<hr>
<p>*using <code>getElements</code> will actually give you a <a href="https://developer.mozilla.org/en-US/docs/Web/API/NodeList" target="_blank">NodeList Object</a>, which is like an array.</p>
</section>
<!--Manipulating the DOM-->
<section>
<h3>Changing Nodes</h3>
<img src="img/two-color.jpg" alt="Red and yellow tulip"/>
<p class="credit">Photo credit: <a href="https://flic.kr/p/bCYp2S" target="_blank">Darryl Kenyon</a> <a href="http://creativecommons.org/licenses/by-nc-sa/2.0/" target="_blank">cc</a>
</section>
<section>
<h3>DOM Nodes: Attributes</h3>
<p>You can access (<code>get</code>) and change (<code>set</code>) attributes of DOM nodes using dot notation.</p><br>
<p>To change this element:</p>
<pre><code class="html"><img id="kittenPic" src="http://placekitten.com/g/200/300" alt="cat"/>
</code></pre>
<p>We could change the src attribute this way:</p>
<pre><code class="javascript">var imgKitten = document.getElementById('kittenPic');
// will return src attribute on image
imgKitten.src
// will set our src to a new src
imgKitten.src = 'http://placekitten.com/g/600/500';</code></pre>
</section>
<section>
<h3>DOM Nodes: Getting and Setting Attributes</h3>
<p>You can also use <code><a href="https://developer.mozilla.org/en-US/docs/Web/API/Element/getAttribute" target="_blank">getAttribute</a></code> or <code><a href="https://developer.mozilla.org/en-US/docs/Web/API/Element/setAttribute" target="_blank">setAttribute</a></code></p>
<pre><code class="html"><img id="kittenPic" src="http://placekitten.com/g/200/300" alt="cat"/>
</code></pre>
<p>We could change the src attribute this way:</p>
<pre><code class="javascript">var imgKitten = document.getElementById('kittenPic');
// will return src attribute on image
imgKitten.getAttribute('src');
// will set our src to a new src
imgKitten.setAttribute('src', 'http://placekitten.com/g/600/500');</code></pre>
</section>
<section>
<h3>DOM Nodes: Styles</h3>
<p>You can change page css using <code>style</code></p><br>
<p>To make this CSS:</p>
<pre><code class="css">body {
color: red;
}
</code></pre>
<p>Use this JavaScript:</p>
<pre><code class="javascript">var pageBody = document.getElementsByTagName('body')[0];
pageBody.style.color = 'red';</code></pre>
</section>
<section>
<h3>DOM Nodes: More Styles</h3>
<p>The rule of thumb in JavaScript is to change CSS styles with a "<code>-</code>" to <a href="https://en.wikipedia.org/wiki/CamelCase" target="_blank">camelCase</a>.</p><br>
<p>To make this CSS:</p>
<pre><code class="css">body {
background-color: pink;
padding-top: 10px;
}
</code></pre>
<p>Use this JavaScript:</p>
<pre><code class="javascript">var pageBody = document.getElementsByTagName('body')[0]
pageBody.style.backgroundColor = 'pink';
pageBody.style.paddingTop = '10px';
</code></pre>
</section>
<section>
<h3>Let's Develop It</h3>
<p>Create a simple HTML page or <a href="files/class4.zip">use this sample code</a>.</p>
<p>Isolate a node (an element on the page) and change an attribute or add a new style.</p>
</section>
<!--Manipulating the DOM-->
<section>
<h3>DOM innerHTML</h3>
<p>Each DOM node has an <code><a href="https://developer.mozilla.org/en-US/docs/Web/API/Element/innerHTML" target="_blank">innerHTML</a></code> property with the HTML and content of its children. You can use the property to view or change the HTML of a node.</p><br>
<p>For example, you can overwrite the entire body:</p>
<pre><code class="javascript">var pageBody = document.getElementsByTagName('body')[0];
pageBody.innerHTML = '<h1>Oh Noes!</h1><p>I changed the whole page!</p>'</code></pre><br>
</section>
<section>
<h3>DOM innerHTML continued</h3>
<p>You can also target one specific element's content</p><br>
<p>To put content in this paragraph element:</p>
<pre><code class="html"><p id="warning"></p></code></pre>
<p>We can select the node and modify it</p>
<pre><code class="javascript">var warningParagraph = document.getElementById('warning');
warningParagraph.innerHTML = 'Danger, Will Robinson!';</code></pre>
</section>
<section>
<h3>Creating New Nodes</h3>
<p>The <code>document</code> object also has methods to create nodes from scratch:</p>
<pre><code class="javascript">document.createElement(tagName);
document.createTextNode(text);
element.appendChild(element);</code></pre>
</section>
<section>
<h3>Creating New Nodes: Sample Code</h3>
<pre><code class="javascript">var pageBody = document.getElementsByTagName('body')[0];
// create our image tag with attributes
var newImg = document.createElement('img');
newImg.src = 'http://placekitten.com/g/500/200';
newImg.style.border = '1px solid black';
// add our image to the body
pageBody.appendChild(newImg);
// create a paragraph tag with content
var newParagraph = document.createElement('p');
var paragraphText = document.createTextNode('Squee!');
newParagraph.appendChild(paragraphText);
// add our new paragraph to the body
pageBody.appendChild(newParagraph);</code></pre>
</section>
<section>
<h3>Let's Develop It</h3>
<p>Create a new paragraph element and add it to a <code>div</code> on your page.</p>
</section>
<!-- Events -->
<section>
<h3>Events</h3>
<img src="img/magician.jpg" alt="Lego Magician" class="noborder"/>
<p class="credit">Photo credit: <a href="https://flic.kr/p/9hBrtv" target="_blank">Eva Peris</a> <a href="http://creativecommons.org/licenses/by-nc/2.0/" target="_blank">cc</a></p>
</section>
<section>
<h3>Events</h3>
<p>An <strong><a href="https://developer.mozilla.org/en-US/docs/Web/Events" target="_blank">event</a></strong> is an object that is sent when actions take place on your webpage, most often when a user interacts with your webpage.</p><br>
<p>For example, JavaScript creates an event when a user clicks an element.</p>
<pre><code class="javascript">element.addEventListener('click', function(event) {
// code to be executed when user clicks
});
</code></pre>
</section>
<section>
<h3>Types of Events</h3>
<p>There are a <a href="https://developer.mozilla.org/en-US/docs/Web/Events" target="_blank">variety of events</a>. Some of the more common events are:</p>
<ul>
<li><strong><a href="https://developer.mozilla.org/en-US/docs/Web/Events/click" target="_blank">click</a>:</strong> Occurs when the user clicks on an element</li>
<li><strong><a href="https://developer.mozilla.org/en-US/docs/Web/Events/mouseover" target="_blank">mouseover</a>:</strong> Occurs when the pointer is moved onto an element</li>
<li><strong><a href="https://developer.mozilla.org/en-US/docs/Web/Events/mouseout" target="_blank">mouseout</a>:</strong> Occurs when the pointer is moved off an element</li>
<li><strong><a href="https://developer.mozilla.org/en-US/docs/Web/Events/keyup" target="_blank">keyup</a>:</strong> Occurs when the user releases a key</li>
<li><strong><a href="https://developer.mozilla.org/en-US/docs/Web/Events/load_(ProgressEvent)" target="_blank">load</a>:</strong> Occurs when a document has been loaded</li>
<li><strong><a href="https://developer.mozilla.org/en-US/docs/Web/Events/focus" target="_blank">focus</a>:</strong> Occurs when an element gets focus</li>
<li><strong><a href="https://developer.mozilla.org/en-US/docs/Web/Events/blur" target="_blank">blur</a>:</strong> Occurs when an element loses focus</li>
</ul>
</section>
<section>
<h3>Calling Functions from HTML</h3>
<p>You can call a function directly from your HTML code:</p>
<pre><code class="html"><button id="myBtn" onclick="sayHi()">Click Me!</button>
</code></pre>
<pre><code class="javascript">function sayHi (event) {
alert('Hi!');
};</code></pre>
</section>
<section>
<h3>Calling Functions from JavaScript</h3>
<p>You can call a function from the addEventListener:</p>
<pre><code class="html"><button id="myBtn">Click Me!</button>
</code></pre>
<pre><code class="javascript">var button = document.getElementById("myBtn");
button.addEventListener("click", function (event) {
alert("Hi!");
});</code></pre>
<p>or</p>
<pre><code class="javascript">var button = document.getElementById("myBtn");
var sayHi = function (event) {
alert("Hi!");
};
button.addEventListener("click", sayHi);</code></pre>
</section>
<section>
<h3>Let's Develop It</h3>
<p>Go back to the sample files you downloaded earlier.</p>
<p>Make some JavaScript code fire after a <code>mouseover</code> event.</p>
</section>
<!-- More Events -->
<!-- <section>
<h3>Preventing Defaults</h3>
<img src="img/donotwant.jpg" alt="A cat resisting a bath"/>
</section>
<section>
<h3>Preventing Defaults</h3>
<p>Elements like links and checkboxes have default behaviors determined by the browser. However, the <code>event</code> object has a built-in method to <a href="https://developer.mozilla.org/en-US/docs/Web/API/Event/preventDefault" target="_blank">prevent the default behavior</a></p>
<p>Our anchor link in HTML</p>
<pre><code class="html"><a id="myLink" href="https://www.girldevelopit.com">GDI</a>
</code></pre>
<p>Code to prevent going to link's href on click</p>
<pre><code class="javascript">var link = document.getElementById("myLink");
link.addEventListener("click", function(event) {
event.preventDefault();
});
</code></pre>
</section>
-->
<!-- <section>
<h3>currentTarget</h3>
<img src="img/arrow.jpg" alt="Lighted arrow sign pointed downward"/>
<p class="credit">Photo credit: <a href="https://flic.kr/p/6ei68A" target="_blank">Alan Berning</a> <a href="http://creativecommons.org/licenses/by-nc/2.0/" target="_blank">cc</a></p>
</section>
<section>
<h3>currentTarget</h3>
<p>The event's <code><a href="https://developer.mozilla.org/en-US/docs/Web/API/Event/currentTarget" target="_blank">currentTarget</a></code> references the element the event listener was attached to.</p>
<p>Our button in HTML:</p>
<pre><code class="html"><button id="myBtn">Click Me!</a></code></pre>
<p>This code adds styles and text to our clicked button</p>
<pre><code class="javascript">myButton = document.getElementById("myBtn");
myButton.addEventListener("click", function(event) {
btn = event.currentTarget;
btn.style.backgroundColor = 'red';
btn.innerHTML = 'Clicked!';
};</code></pre>
<p>You may also see code that references the keyword <code><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/this" target="_blank">this</a></code> as the "target".
</section> -->
<!-- <section>
<h3>Let's Develop It</h3>
<p>Write code that targets this link:</p>
<pre><code class="html"><a href="http://girldevelopit.com/" id="gdiLink">Girl Develop It</a>
</code></pre>
<p>When a user clicks the link, the page should display an error message instead of going to the Girl Develop It homepage.</p>
</section> -->
<!-- User input -->
<!-- <section>
<h3>User Input</h3>
<img src="img/comment-box.jpg" alt="Comment box"/>
<p class="credit">Photo credit: <a href="https://flic.kr/p/fnZ4RT" target="_blank">Rym DeCoster</a> <a href="http://creativecommons.org/licenses/by-nc/2.0/" target="_blank">cc</a></p>
</section>
<section>
<h3>Forms</h3>
<p>You can collect information from users to use in your code. The most common method is an HTML form.</p>
<pre><code class="html"><form id="userForm">
<label for="name">First Name:</label>
<input type="text" id="firstName"/>
<input type="radio" name="married" value="Yes" checked /> Yes
<input type="radio" name="married" value="No" /> No
<input type="submit" id="submitBtn" value="Submit" />
</form>
</code></pre>
</section>
<section>
<h3>Retrieving Form Data</h3>
<p>You retrieve the values of form elements using the <code>value</code> method.</p>
<pre><code class="javascript">var name = document.getElementById('firstName').value;
console.log(name);
</code></pre>
<p>You can retrieve the value of a form at any time, even when an event like <code>blur</code> is triggered (when a form element loses focus).</p>
</section>
<section>
<h3>Radio Buttons</h3>
<p>Radio buttons usually do not have IDs, so you would need to use a <code>for</code> loop to get the value on each radio:</p>
<pre><code class="javascript">var radios = document.getElementsByName('married');
var length = radios.length;
for (var i = 0; i < length; i++) {
if (radios[i].checked) {
var radioButtonValue = radios[i].value;
// only one radio can be checked, so stop now
break;
}
}
</code></pre>
</section>
<section>
<h3>Submit buttons</h3>
<p>If you are going to retrieve form values with the submit button, be sure to prevent the default action!</p>
<pre><code class="javascript">var submitButton = document.getElementById('submitBtn');
submitButton.addEventListener("click", function(event) {
event.preventDefault();
var name = document.getElementById('firstName').value;
console.log(name);
})
</code></pre>
</section>
<section>
<h3>Let's Develop It</h3>
<p>Collect a value from the input box on the page. Use it inside a function of some kind. For example, collect a number and multiply it by five or collect a name and display a greeting.</p>
</section>
<!-- Final slides-->
<section>
<h3>You did it!</h3>
<img src="img/jumping-man.jpg" alt="Man jumping in air"/>
<p class="credit">Photo credit: <a href="http://www.flickr.com/photos/sunface13/988453859/" target="_blank">sunface13</a> <a href="http://creativecommons.org/licenses/by-nc/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>
<li><a href="https://www.khanacademy.org/computing/cs/programming" target="_blank">Khan Academy</a> has a lot more information abut drawing and animations.</li>
</ul>
</section>
<section>
<h2>Questions?</h2>
</section>
</div>
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Intro to JavaScript -- Girl Develop It --
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