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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">
<meta name="author" content="Girl Develop It">
<meta name="apple-mobile-web-app-capable" content="yes" />
<meta name="apple-mobile-web-app-status-bar-style" content="black-translucent" />
<link rel="stylesheet" href="css/reveal.css">
<link rel="stylesheet" href="css/theme/simple.css" id="theme">
<link rel="stylesheet" href="css/custom.css">
<!-- For syntax highlighting -->
<!-- light editor --> <link rel="stylesheet" href="lib/css/light.css">
<!-- dark editor <link rel="stylesheet" href="lib/css/dark.css">-->
<!-- <link rel="stylesheet" href="lib/css/zenburn.css">-->
<link rel="stylesheet" href="plugin/accessibility-helper/css/accessibility-helper.css">
<!-- If the query includes 'print-pdf', include the PDF print sheet -->
<script>
if( window.location.search.match( /print-pdf/gi ) ) {
var link = document.createElement( 'link' );
link.rel = 'stylesheet';
link.type = 'text/css';
link.href = 'css/print/pdf.css';
document.getElementsByTagName( 'head' )[0].appendChild( link );
}
</script>
<!-- If use the PDF print sheet so students can print slides-->
<link rel="stylesheet" href="css/print/pdf.css" type="text/css" media="print">
<link rel="icon" type="image/x-icon" href="favicon.ico" />
<!--[if lt IE 9]>
<script src="lib/js/html5shiv.js"></script>
<![endif]-->
</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 4</h2>
</section>
<!-- Review: Role of HTML v. CSS-->
<section>
<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/">Ginable</a> <a href="http://creativecommons.org/licenses/by-nc-sa/2.0/">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/">Nic's events</a> <a href="http://creativecommons.org/licenses/by-nc-sa/2.0/">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/">pumpkincat210</a> <a href="http://creativecommons.org/licenses/by-nc-sa/2.0/">cc</a>
</section>
<section>
<h3>IDs vs. Classes</h3>
<p><strong>ID</strong> -- Should only apply to one element on a webpage, i.e., a webpage only has one footer.<br />
The "#" is how you tell CSS "this is an id."</p>
<p><strong>Class</strong> -- Lots of elements can have the same class, i.e., There can be many warnings on one webpage.<br />
The "." is how you tell CSS "this is a class name."</p>
</section>
</section>
<!--The DOM-->
<section>
<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/">cc</a>
</section>
<section>
<h3>The DOM Tree</h3>
<p>We model the nested structure of an HTML page with the DOM (Document Object Model) Tree. The browser makes a "map" of all the elements on a page.</p>
</section>
<section>
<h3>The DOM: Sample Code</h3>
<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: Sample Model</h3>
<img src="img/dom-tree.png" alt="Simple DOM Tree"/>
</section>
</section>
<!--Accessing the DOM-->
<section>
<section>
<h3>DOM Access</h3>
<p>Your browser automatically builds a Document object to store the DOM of a page. To change a page:</p>
<ol>
<li>Find the DOM node and store it in a variable</li>
<li>Use methods to manipulate the node</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">Jeffery Beall</a> <a href="http://creativecommons.org/licenses/by-nc-sa/2.0/">cc</a>
</section>
<section>
<h3>DOM Access: By Id</h3>
<p>You can find nodes by id using the method:</p>
<pre><code class="js">document.getElementById(id);
</code></pre>
<p>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="js">var imgKitten=document.getElementById('kittenPic');
</code></pre>
</section>
<section>
<h3>DOM Access: By Tag Name</h3>
<p>You can certain types of HTML elements using this method:</p>
<pre><code class="js">document.getElementsByTagName(tagName);
</code></pre>
<p>To find:</p>
<pre><code class="html"><li>Daisy</li>
<li>Tulip</li>
</code></pre>
<p>We would use:</p>
<pre><code class="js">var listItems=document.getElementsByTagName('li');
for (var i=0; i < listItems.length; i++) {
var listItem=listItems[i];
}
</code></pre>
</section>
<section>
<h3>DOM Access: HTML 5</h3>
<p>In newer browsers, you can use other methods too.</p>
<p>Available in <a href="http://caniuse.com/#search=getElementsByClassName">IE9+, FF3.6+, Chrome 17+, Safari 5+</a>:</p>
<pre><code class="js">document.getElementsByClassName(className);
</code></pre>
<p>Available in <a href="http://caniuse.com/#search=querySelectorAll">IE8+, FF3.6+, Chrome 17+, Safari 5+</a>:</p>
<pre><code class="js">document.querySelector(cssQuery);
document.querySelectorAll(cssQuery);
</code></pre>
</section>
<section>
<h3>getElement vs. getElements</h3>
<p>Any method that starts with "getElement" will return a <span class="blue">single</span> node.</p>
<pre><code class="js">document.getElementById('uniqueID'); //returns a single node
</code></pre>
<p>Any method that starts with "getElements" will return a <span class="blue">array</span> of nodes. To modify a single node, you will need to use bracket notation to select the correct one.</p>
<pre><code class="js">document.getElementsByTagName('p'); //returns multiple nodes
var specficParagraph=document.getElementsByTagName('p')[2];
</code></pre>
</section>
</section>
<!--Manipulating the DOM-->
<section>
<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">Darryl Kenyon</a> <a href="http://creativecommons.org/licenses/by-nc-sa/2.0/">cc</a>
</section>
<section>
<h3>DOM Nodes: Attributes</h3>
<p>You can access and change attributes of DOM nodes using dot notation.</p>
<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="js">var imgKitten=document.getElementById('kittenPic');
var oldSrc=imgKitten.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>getAttribute/setAttribute</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="js">var imgKitten=document.getElementById('kittenPic');
var oldSrc=imgKitten.getAttribute('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>
<p>To make this CSS:</p>
<pre><code class="css">body {
color: red;
}
</code></pre>
<p>Use this JavaScript:</p>
<pre><code class="js">var pageNode=document.getElementsByTagName('body')[0];
pageNode.style.color='red';
</code></pre>
</section>
<section>
<h3>DOM Nodes: More Styles</h3>
<p>Change any CSS property with a "-" to camelCase, and be sure to include a unit on any number</p>
<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="js">var pageNode=document.getElementsByTagName('body')[0]
pageNode.style.backgroundColor='pink';
pageNode.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>
</section>
<!--Manipulating the DOM-->
<section>
<section>
<h3>DOM innerHTML</h3>
<p>Each DOM node has an <code>innerHTML</code> property with the HTML of all its children. You can use the property to view or change the HTML of a node.</p>
<p>For example, you can overwrite the entire body:</p>
<pre><code class="js">var pageNode=document.getElementsByTagName('body')[0];
pageNode.innerHTML='<h1>Oh Noes!</h1>
<p>I just changed the whole page!</p>'
</code></pre>
<p>Or just add some new content to the end</p>
<pre><code class="js">pageNode.innerHTML +='...just adding this bit at the end of the page.';
</code></pre>
</section>
<section>
<h3>DOM innerHTML continued</h3>
<p>You can also target a particular element</p>
<p>To fill this HTML 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="js">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 provides ways to create nodes from scratch:</p>
<pre><code class="js">document.createElement(tagName);
document.createTextNode(text);
document.appendChild();
</code></pre>
</section>
<section>
<h3>Creating New Nodes: Sample Code</h3>
<pre><code class="js">var pageNode=document.getElementsByTagName('body')[0];
var newImg=document.createElement('img');
newImg.src='http://placekitten.com/g/500/200';
newImg.style.border='1px solid black';
pageNode.appendChild(newImg);
var newParagraph=document.createElement('p');
var paragraphText=document.createTextNode('Squee!');
newParagraph.appendChild(paragraphText);
pageNode.appendChild(newParagraph);
</code></pre>
</section>
<section>
<h3>Let's Develop It</h3>
<p>Create a new paragraph element and add it to a div on your page.</p>
</section>
</section>
<!-- Events -->
<section id="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 'event' is a type of object that is created when the user interacts with a web page.</p>
<p>For example, JS creates an event when a user clicks an element.</p>
<pre><code class="js">element.onclick=function () {
//code to execute when the click happens
};
</code></pre>
</section>
<section>
<h3>Types of Events</h3>
<p>There are <a href="http://www.w3schools.com/jsref/dom_obj_event.asp">variety of events</a>. Some of the most common:</p>
<ul>
<li><strong>onclick:</strong> The event occurs when the user clicks on an element</li>
<li><strong>onmouseover:</strong> The event occurs when the pointer is moved onto an element</li>
<li><strong>onkeyup:</strong> The event occurs when the user releases a key</li>
<li><strong>onload:</strong> The event occurs when a document has been loaded</li>
<li><strong>onfocus:</strong> The event occurs when an element gets focus</li>
</ul>
</section>
<section>
<h3>Events and Code</h3>
<p>How do you make an event trigger some code?</p>
<ol>
<li>Break your code into functions</li>
<li>Associate a function with a JavaScript event</li>
</ol>
</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="clickMe" onclick="sayHi()">Click Me!</button>
</code></pre>
<pre><code class="js">function sayHi() {
alert ('Hi!');
}
</code></pre>
</section>
</section>
<!-- Listening Functions -->
<section>
<section>
<h3>Listening Functions</h3>
<img src="img/ear.jpg" alt="Ear"/>
<p class="credit">Photo credit: <a href="https://flic.kr/p/58bycz" target="_blank">Simon James</a> <a href="http://creativecommons.org/licenses/by-nc/2.0/" target="_blank">cc</a></p>
</section>
<section>
<h3>Listening Functions</h3>
<p>Listening functions work like many of the other things we have done. First, find the object:</p>
<pre><code class="js">var myTarget=document.getElementById('clickMe');
</code></pre>
<p>Then add an event to that object:</p>
<pre><code class="js">myTarget.onclick=function(){
alert ('Hi!');
}
</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 an <code>onmouseover</code> event. Try adding the event to the HTML and adding a listening function.</p>
</section>
</section>
<!-- More Events -->
<section id="events2">
<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 buttons and links have a default behaviors. However, the <code>event</code> objects has a built-in method to handle that:</p>
<pre><code class="js">element.onclick=function (event) {
event.preventDefault();
};
</code></pre>
</section>
<section>
<h3>This</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>This</h3>
<p>The keyword <code>this</code> references the element that the user has just interacted with</p>
<pre><code class="js">element.onmouseover=function (event) {
console.log(this);
};
element.onclick=function (event) {
this.style.backgroundColor='red';
this.innerHTML='I've been clicked!';
};
</code></pre>
</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>
</section>
<!-- User input -->
<section id="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 functions. The most common method is an HTML form</p>
<pre><code class="html"><form id="temperatureForm">
<label for="temp">Temperature:</label> <input type="text" id="temp" size="3"/> degrees in
<input type="radio" name="tempFormat" value="F" checked />Fahrenheit
<input type="radio" name="tempFormat" value="C" />Celsius <br />
<label for="submitButton"></label> <input id="tempSubmitButton" type="submit" 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="js">var temperature=document.getElementById('temp').value;
console.log (temperature);
</code></pre>
<p>You can retrieve the value of a form at any time. Try <code>onblur</code> (when a form element loses focus).</p>
</section>
<section>
<h3>Radio Buttons</h3>
<p>Radio buttons usually do not have IDs, so you will need to use an array:</p>
<pre><code class="js">var radios=document.getElementsByName('tempFormat');
for (var i=0, length=radios.length; 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="js">var submitButton=document.getElementById('tempSubmitButton');
submitButton.onclick=function () {
event.preventDefault();
var temperature=document.getElementById('temp').value;
console.log (temperature);
}
</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>
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<!-- Final slides-->
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<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">Khan Academy</a> has a lot more information abut drawing and animations.</li>
</ul>
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<h2>Questions?</h2>
</section>
</section>
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Intro to JavaScript -- Girl Develop It --
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