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Lecture 0 - CS50's Web Programming with Python and JavaScript.htm
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Lecture 0 - CS50's Web Programming with Python and JavaScript.htm
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<!DOCTYPE html>
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<meta name="viewport" content="initial-scale=1, width=device-width"><meta property="og:description" content="This course picks up where Harvard University's CS50 leaves off, diving more deeply into the design and implementation of web apps with Python, JavaScript, and SQL using frameworks like Django, React, and Bootstrap. Topics include database design, scalability, security, and user experience. Through hands-on projects, students learn to write and use APIs, create interactive UIs, and leverage cloud services like GitHub and Heroku. By semester’s end, students emerge with knowledge and experience in principles, languages, and tools that empower them to design and deploy applications on the Internet.">
<meta property="og:image" content="https://img.youtube.com/vi/24Kf3v7kZyE/maxresdefault.jpg"><meta property="og:title" content="Lecture 0 - CS50's Web Programming with Python and JavaScript">
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<a data-id="" id="lecture-0" style="top: -81.3333px;"></a><h1 class="no_toc"><a data-id="" href="#lecture-0">Lecture 0</a></h1>
<ul id="markdown-toc">
<li><a href="#introduction" id="markdown-toc-introduction">Introduction</a></li>
<li><a href="#web-programming" id="markdown-toc-web-programming">Web Programming</a></li>
<li><a href="#html-hypertext-markup-language" id="markdown-toc-html-hypertext-markup-language">HTML (Hypertext Markup Language)</a> <ul>
<li><a href="#document-object-model-dom" id="markdown-toc-document-object-model-dom">Document Object Model (DOM)</a></li>
<li><a href="#more-html-elements" id="markdown-toc-more-html-elements">More HTML Elements</a></li>
<li><a href="#forms" id="markdown-toc-forms">Forms</a></li>
</ul>
</li>
<li><a href="#css-cascading-style-sheets" id="markdown-toc-css-cascading-style-sheets">CSS (Cascading Style Sheets)</a></li>
<li><a href="#responsive-design" id="markdown-toc-responsive-design">Responsive Design</a></li>
<li><a href="#bootstrap" id="markdown-toc-bootstrap">Bootstrap</a></li>
<li><a href="#sass-syntactically-awesome-style-sheets" id="markdown-toc-sass-syntactically-awesome-style-sheets">Sass (Syntactically Awesome Style Sheets)</a></li>
</ul>
<a data-id="" id="introduction" style="top: -81.3333px;"></a><h2><a data-id="" href="#introduction">Introduction</a></h2>
<p>In this course, we’re picking up where CS50 left off and diving into
the design and creation of web applications. We’ll build our web-design
skills by working on a number of projects throughout the course,
including an open-ended final project where you’ll have the chance to
create a website of your own!</p>
<p>In this course, you’ll need a text editor where you can write code locally on your computer. Some popular ones include <a href="https://code.visualstudio.com/">Visual Studios Code</a>, <a href="https://www.sublimetext.com/">Sublime Text</a>, <a href="https://atom.io/">Atom</a>, and <a href="https://www.vim.org/">Vim</a>, but there are many more to choose from!</p>
<a data-id="" id="web-programming" style="top: -81.3333px;"></a><h2><a data-id="" href="#web-programming">Web Programming</a></h2>
<p><strong>Course Topics:</strong> We’ll go into more detail later, but here’s a brief overview of what we’ll be working on during this course:</p>
<ol>
<li><strong>HTML and CSS</strong> (a markup language used to outline a webpage, and a procedure for making our sites more visually appealing)</li>
<li><strong>Git</strong> (used for version control and collaboration)</li>
<li><strong>Python</strong> (a widely-used programming language we’ll use to make our sites more dynamic)</li>
<li><strong>Django</strong> (a popular web framework we’ll use for the backend of our sites)</li>
<li><strong>SQL, Models, and Migrations</strong> (a language used for
storing and retrieving data, and Django-specific methods that make it
easier to interact with SQL databases)</li>
<li><strong>JavaScript</strong> (a programming language used to make websites faster and more interactive)</li>
<li><strong>User Interfaces</strong> (methods used to make a website as easy to use as possible)</li>
<li><strong>Testing, CI, CD</strong> (learning about different methods used to make sure updates to web pages proceed smoothly)</li>
<li><strong>Scalability and Security</strong> (making sure our websites can be accessed by many users at once, and that they are safe from malicious intent)</li>
</ol>
<a data-id="" id="html-hypertext-markup-language" style="top: -81.3333px;"></a><h2><a data-id="" href="#html-hypertext-markup-language">HTML (Hypertext Markup Language)</a></h2>
<ul class="fa-ul">
<li data-marker="*"><span class="fa-li"><i class="fas fa-square"></i></span>HTML
is a markup language that defines the structure of a web page. It is
interpreted by your web browser (Safari, Google Chrome, Firefox, etc.)
in order to display content on your screen.</li>
<li data-marker="*"><span class="fa-li"><i class="fas fa-square"></i></span>Let’s get started by writing a simple HTML file!</li>
</ul>
<div class="language-html highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="cp"><!DOCTYPE html></span>
<span class="nt"><html</span> <span class="na">lang=</span><span class="s">"en"</span><span class="nt">></span>
<span class="nt"><head></span>
<span class="nt"><title></span>Hello!<span class="nt"></title></span>
<span class="nt"></head></span>
<span class="nt"><body></span>
Hello, world!
<span class="nt"></body></span>
<span class="nt"><html></span>
</code></pre></div></div>
<ul class="fa-ul">
<li data-marker="*"><span class="fa-li"><i class="fas fa-square"></i></span>When we open up this file in our browser, we get:</li>
</ul>
<p><img src="Lecture%200%20-%20CS50's%20Web%20Programming%20with%20Python%20and%20JavaScript_files/hello0.png" alt="Hello Page"></p>
<ul class="fa-ul">
<li data-marker="*"><span class="fa-li"><i class="fas fa-square"></i></span>Now, let’s take some time to talk about the file we just wrote, which seems to be pretty complicated for such a simple page.
<ul class="fa-ul">
<li data-marker="*"><span class="fa-li"><i class="fas fa-square"></i></span>In the first line, we are declaring (to the web browser) that we are writing the document in the latest version of HTML: HTML5.</li>
<li data-marker="*"><span class="fa-li"><i class="fas fa-square"></i></span>After that, the page consists of nested <strong>HTML elements</strong> (such as html and body), each with an <strong>opening and closing tag</strong> marked with either <code class="language-plaintext highlighter-rouge"><element></code> for an opening and <code class="language-plaintext highlighter-rouge"></element></code> for a closing.</li>
<li data-marker="*"><span class="fa-li"><i class="fas fa-square"></i></span>Notice
how each of the inner elements is indented just a bit further than the
last. While this is not necessarily required by the browser, it will be
very helpful to keep this up in your own code.</li>
<li data-marker="*"><span class="fa-li"><i class="fas fa-square"></i></span>HTML elements can include <strong>attributes</strong>, which give the browser extra information about the element. For example, when we include <code class="language-plaintext highlighter-rouge">lang="en"</code> in our initial tag, we are telling the browser that we are using English as our primary language.</li>
<li data-marker="*"><span class="fa-li"><i class="fas fa-square"></i></span>Inside the HTML element, we typically want to include both a <code class="language-plaintext highlighter-rouge">head</code> and a <code class="language-plaintext highlighter-rouge">body</code>
tag. The head element will include information about your page that is
not necessarily displayed, and the body element will contain what is
actually visible to users who visit the site.</li>
<li data-marker="*"><span class="fa-li"><i class="fas fa-square"></i></span>Within the head, we have included a <code class="language-plaintext highlighter-rouge">title</code> for our webpage, which you’ll notice is displayed in the tab at the top of our web browser.</li>
<li data-marker="*"><span class="fa-li"><i class="fas fa-square"></i></span>Finally, we’ve included the text “Hello, world!” in the body, which is the visible part of our page.</li>
</ul>
</li>
</ul>
<a data-id="" id="document-object-model-dom" style="top: -81.3333px;"></a><h3><a data-id="" href="#document-object-model-dom">Document Object Model (DOM)</a></h3>
<p><img src="Lecture%200%20-%20CS50's%20Web%20Programming%20with%20Python%20and%20JavaScript_files/dom.png" alt="DOM"></p>
<ul class="fa-ul">
<li data-marker="*"><span class="fa-li"><i class="fas fa-square"></i></span>The
DOM is a convenient way of visualizing the way HTML elements relate to
each other using a tree-like structure. Above is an example of the DOM
layout for the page we just wrote.</li>
</ul>
<a data-id="" id="more-html-elements" style="top: -81.3333px;"></a><h3><a data-id="" href="#more-html-elements">More HTML Elements</a></h3>
<ul class="fa-ul">
<li data-marker="*"><span class="fa-li"><i class="fas fa-square"></i></span>There
are many HTML elements you may want to use to customize your page,
including headings, lists, and bolded sections. In this next example,
we’ll see a few of of these in action.</li>
<li data-marker="*"><span class="fa-li"><i class="fas fa-square"></i></span>One more thing to note: <code class="language-plaintext highlighter-rouge"><!-- --></code> gives us a comment in HTML, so we’ll use that below to explain some of the elements.</li>
</ul>
<pre><code class="language-HTML"><!DOCTYPE html>
<html lang="en">
<head>
<title>HTML Elements</title>
</head>
<body>
<!-- We can create headings using h1 through h6 as tags.
-->
<h1>A Large Heading</h1>
<h2>A Smaller Heading</h2>
<h6>The Smallest Heading</h6>
<!-- The strong and i tags give us bold and italics
respectively. -->
A <strong>bold</strong> word and an
<i>italicized</i> word!
<!-- We can link to another page (such as cs50's page) using
a. -->
View the <a href="https://cs50.harvard.edu/">CS50
Website</a>!
<!-- We used ul for an unordered list and ol for an ordered
one. both ordered and unordered lists contain li, or list items. -->
An unordered list:
<ul>
<li>foo</li>
<li>bar</li>
<li>baz</li>
</ul>
An ordered list:
<ol>
<li>foo</li>
<li>bar</li>
<li>baz</li>
</ol>
<!-- Images require a src attribute, which can be either the
path to a file on your computer or the link to an image online. It also
includes an alt attribute, which gives a description in case the image
can't be loaded. -->
An image:
<img src="../../images/duck.jpeg" alt="Rubber Duck
Picture">
<!-- We can also see above that for some elements that don't
contain other ones, closing tags are not necessary. -->
<!-- Here, we use a br tag to add white space to the page.
-->
<br/> <br/>
<!-- A few different tags are necessary to create a table.
-->
<table>
<thead>
<th>Ocean</th>
<th>Average Depth</th>
<th>Maximum Depth</th>
</thead>
<tbody>
<tr>
<td>Pacific</td>
<td>4280 m</td>
<td>10911 m</td>
</tr>
<tr>
<td>Atlantic</td>
<td>3646 m</td>
<td>8486 m</td>
</tr>
</tbody>
</table>
</body>
<html>
</code></pre>
<p>This page, when rendered, looks something like this:</p>
<p><img src="Lecture%200%20-%20CS50's%20Web%20Programming%20with%20Python%20and%20JavaScript_files/elements.png" alt="Elements"></p>
<ul class="fa-ul">
<li data-marker="*"><span class="fa-li"><i class="fas fa-square"></i></span>In
case you’re worried about it, know that you’ll never have to memorize
these elements. It’s very easy to simply search something like “image in
HTML” to find the <code class="language-plaintext highlighter-rouge">img</code> tag. One resource that’s especially helpful for learning about these elements is <a href="https://www.w3schools.com/html/html_elements.asp">W3 Schools</a>.</li>
</ul>
<a data-id="" id="forms" style="top: -81.3333px;"></a><h3><a data-id="" href="#forms">Forms</a></h3>
<ul class="fa-ul">
<li data-marker="*"><span class="fa-li"><i class="fas fa-square"></i></span>Another
set of elements that is really important when creating a website is how
to collect information from users. You can allow users to enter
information using an HTML form, which can contain several different
types of input. Later in the course, we’ll learn about how to handle
information once a form has been submitted.</li>
<li data-marker="*"><span class="fa-li"><i class="fas fa-square"></i></span>Just as with other HTML elements, there’s no need to memorize these, and W3 Schools is a great resource for learning about them!</li>
</ul>
<div class="language-html highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="cp"><!DOCTYPE html></span>
<span class="nt"><html</span> <span class="na">lang=</span><span class="s">"en"</span><span class="nt">></span>
<span class="nt"><head></span>
<span class="nt"><title></span>Forms<span class="nt"></title></span>
<span class="nt"></head></span>
<span class="nt"><body></span>
<span class="nt"><form></span>
<span class="nt"><input</span> <span class="na">type=</span><span class="s">"text"</span> <span class="na">placeholder=</span><span class="s">"First Name"</span> <span class="na">name=</span><span class="s">"first"</span><span class="nt">></span>
<span class="nt"><input</span> <span class="na">type=</span><span class="s">"password"</span> <span class="na">placeholder=</span><span class="s">"Password"</span> <span class="na">name=</span><span class="s">"password"</span><span class="nt">></span>
<span class="nt"><div></span>
Favorite Color:
<span class="nt"><input</span> <span class="na">name=</span><span class="s">"color"</span> <span class="na">type=</span><span class="s">"radio"</span> <span class="na">value=</span><span class="s">"blue"</span><span class="nt">></span> Blue
<span class="nt"><input</span> <span class="na">name=</span><span class="s">"color"</span> <span class="na">type=</span><span class="s">"radio"</span> <span class="na">value=</span><span class="s">"green"</span><span class="nt">></span> Green
<span class="nt"><input</span> <span class="na">name=</span><span class="s">"color"</span> <span class="na">type=</span><span class="s">"radio"</span> <span class="na">value=</span><span class="s">"yellow"</span><span class="nt">></span> Yellow
<span class="nt"><input</span> <span class="na">name=</span><span class="s">"color"</span> <span class="na">type=</span><span class="s">"radio"</span> <span class="na">value=</span><span class="s">"red"</span><span class="nt">></span> Red