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<p>Now you can create a dashboard in just a matter of seconds.</p>
<time datetime="2019-10-16">October 16, 2019</time>
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<time datetime="2019-10-15">October 15, 2019</time>
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<p>British scientists have discovered that the ability of software to function directly depends on the presence of infinite loops in it.</p>
<time datetime="2019-10-14">October 14, 2019</time>
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<h3>THE SHOCKING TRUTH! Secret aerial footage taken by a reconnaissance drone</h3>
<p>No one expected that THIS was going on behind the walls…</p>
<time datetime="2019-10-13">October 13, 2019</time>
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<time datetime="2019-10-12">October 12, 2019</time>
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<h3>An unexpected discovery.</h3>
<p>It turns out that in order to start learning JavaScript, you don’t have to be a cat.</p>
<time datetime="2019-10-11">October 11, 2019</time>
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2.334.725-.13.837-1.46.93-2.13h.112c.937.492 1.647 1.33 1.98 2.334-.388.176-.793.31-1.21.4zm18.365-2.864c-1.104-.145-2.215-.232-3.33-.26-.546-.01-1.093.05-1.626.176-1.166.483-2.08 1.425-2.53 2.604l-.158.79 1.795.623c.558.153 1.132.24 1.71.26h.28c3.245-.177 4.137-3.72 4.137-3.72l.084-.353zm-1.264 1.86c-.54 1.394-2.882 1.646-2.966 1.646-.517-.02-1.03-.11-1.525-.26-.186-.085-.633-.26-1.08-.43.374-.966 1.117-1.746 2.065-2.165 0 .68.158 1.953.81 2.083.65.13.613-1.535.566-2.26.934.005 1.865.064 2.79.177-.11.316-.473.65-.66 1.17z" fill="#151841"/><path d="M19.26 39.27c.535 1.362 1.56 2.473 2.874 3.115.534.312 1.204-.07 1.207-.69.002-.285-.15-.55-.397-.695-.918-.46-1.65-1.222-2.073-2.158-.344-.957-1.972-.52-1.61.428zm29.45 3.125c1.083-.59 2.01-1.428 2.706-2.446.3-.556-.112-1.228-.743-1.21-.293.007-.56.17-.698.428-.568.776-1.306 1.412-2.158 1.86-.394.23-.517.742-.27 1.125.263.376.773.482 1.163.242z" fill="#EFA75B" stroke-width="13"/><path d="M16.025 32.436c1.525-1.386 2.427-4.408 2.79-6.835-.084.354 2.613.43 4.138-1.208 1.078-1.125.446-2-.186-3.375-1.71-3.552-4.585-6.323-7.384-8.918-.716-.69-1.44-2.428-2.706-2-.995.353-.93 3.2-.716 4.073 1.09 7.448 4.065 18.263 4.065 18.263zm37.372-.78c-1.704-1.826-2.822-4.12-3.208-6.585 0 .354-2.614.354-4.056-1.29-.995-1.127-.362-1.86.363-3.117 1.86-3.198 4.863-5.718 7.746-8.136.81-.604 1.627-1.47 2.79-.93.994.428.715 2.334.548 3.115-1.083 5.72-2.48 11.376-4.183 16.943z" fill="#FFF"/><path d="M53.564 20.422c-1.98.51-4.138 1.636-5.105 3.487-.43-2.196 1.645-4.65 3.393-5.832.333-.21.312-.703-.037-.886-.162-.085-.357-.076-.512.022-2.157 1.562-4.417 4.5-3.784 7.188.076.262.354.41.614.325l-.075.28c-.085.603.93.864.994.26.446-2.158 2.706-3.376 4.77-3.897.372-.076.522-.526.27-.81-.133-.15-.342-.204-.53-.138zM17.457 18.06c-.55-.354-.995.428-.55.865 1.433 1.004 3.182 3.05 3.395 4.956-.93-1.86-3.05-2.975-5.105-3.486-.386-.005-.633.41-.445.747.042.076.103.14.176.184 2.073.52 4.324 1.73 4.77 3.896.106.328.5.46.78.26.273.192.653.06.745-.26.735-2.66-1.6-5.728-3.766-7.16z" fill="#F1662A"/></svg></span><p class="course-loading-overlay__message"><b class="course-loading-overlay__message-title">Loading…</b><br><span class="course-loading-overlay__message-text">Everything will be ready in few seconds</span></p></div></div><div class="course-layout__sidebar course-theory"><div class="course-theory__inner course-theory__inner--left-stub"><button class="course-theory__close icon-close icon-close--light" type="button">Close</button><ul class="course-tabs course-tabs--non-interactive course-layout__theory-heading js--theory-tabs"><li class="course-tabs__item course-tabs__item--external course-tab course-tab--centered"><span class="course-tab__icon"><svg aria-hidden="true"><use xlink:href="/img/sprites/courses.svg#icon-theory"></use></svg></span><span class="course-tab__title">Theory</span></li><li class="course-tabs__item course-tabs__item--internal course-tab course-tab--centered course-tab--active js--theory-tab__theory"><span class="course-tab__icon"><svg aria-hidden="true"><use xlink:href="/img/sprites/courses.svg#icon-theory"></use></svg></span><span class="course-tab__title">Theory</span></li><li class="course-tabs__item course-tabs__item--internal course-tab course-tab--centered js--theory-tab__comments"><span class="course-tab__icon"><svg aria-hidden="true" style="width: 16px; height: 16px; fill: #2e2c9c;"><use xlink:href="/img/sprites/up.svg#comment"></use></svg></span><span class="course-tab__title">Comments</span></li></ul><section class="course-theory__content"><div class="js--theory-pane__theory course-theory__content-inner"><h1 class="course-theory__content-heading">Why is JavaScript necessary?</h1><div class="course-theory__content-text"><p>Hi, there! Have you decided that you want to learn JavaScript? Excellent choice!</p><p>The JavaScript programming language was invented specifically for the purpose of creating interactive websites. These are websites that respond to user actions. You use interactive features all the time—when you click on the “heart” icon to like something, or upload new posts to your social media feed, when you get to the end of the page, or when you receive new message alerts. You need JavaScript in order to do these things. Today JavaScript is one of the most popular programming languages, so it will come in handy for every web developer.</p><p>In this chapter we will be working with layout. If you don’t yet know how web pages are structured, then we recommend that you take the “<a href="/courses/intro-to-web-development/html-and-css">Introduction to HTML and CSS</a>” chapter first.</p><p>We call JavaScript code a “script”, a computer science term for a language that runs inside a special environment — in our case, the browser. It is saved in a separate file with the extension <code>js</code> (e.g., <code>myScript.js</code> or <code class="nowrap">awesome-effects.js</code>). In order to run this script, this file needs to be included in a page. HTML has a special tag for adding JavaScript:</p><pre><code><script src="file_address"></script></code></pre><p>The script is usually included at the very end of the page, before the closing tag <code></body></code>. For example:</p><pre><code><body>
<!-- Page contents -->
<mark><script src="app.js"></script></mark>
</body></code></pre><p>Let’s explore the main page of a news site as well as the script that was written for it. You can see the code in the editor to the left, and the page itself is displayed on the right in the mini-browser. Let’s include the script and see what can be done using JavaScript.</p></div></div><div class="js--theory-pane__comments hidden course-theory__content-inner"><div class="course-theory__content-text"><h2 class="course-theory__content-heading">Comments</h2><div id="disqus_thread"></div><script>
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<h3>New graphics library</h3>
<p>Now you can create a dashboard in just a matter of seconds.</p>
<time datetime="2019-10-16">October 16, 2019</time>
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<h3>What is going on with robots?</h3>
<p>A lot of interesting things are happening in robotics. This could be a piece of news about the latest developments, but that is not what this is.</p>
<time datetime="2019-10-15">October 15, 2019</time>
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<h3>Infinite loops: It’s time to end them</h3>
<p>British scientists have discovered that the ability of software to function directly depends on the presence of infinite loops in it.</p>
<time datetime="2019-10-14">October 14, 2019</time>
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<h3>THE SHOCKING TRUTH! Secret aerial footage taken by a reconnaissance drone</h3>
<p>No one expected that THIS was going on behind the walls…</p>
<time datetime="2019-10-13">October 13, 2019</time>
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<h3>From the world of psychology</h3>
<p>Studies show that if you do more, you can actually get more done.</p>
<time datetime="2019-10-12">October 12, 2019</time>
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<h3>An unexpected discovery.</h3>
<p>It turns out that in order to start learning JavaScript, you don’t have to be a cat.</p>
<time datetime="2019-10-11">October 11, 2019</time>
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color: #6653d9;
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background: url("img/arrow-back-light.svg") no-repeat 0 0;
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color: #6653d9;
border: 1px solid #6653d9;
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background-image: url("img/moon-normal.svg");
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color: #ffffff;
background-color: #6653d9;
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}
.light-theme .menu-open {
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background-color: #6653d9;
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.light-theme .row-view::before {
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.light-theme .tile-view::before {
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box-shadow: 0 1px 4px rgba(0, 0, 0, 0.2);
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background-color: #fdeacd;
box-shadow: 0 -1px 4px rgba(0, 0, 0, 0.2);
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background-color: #6653d9;
color: #ffffff;
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.light-theme .page-footer {
background-color: #6653d9;
color: #ffffff;
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.light-theme .subscription {
background-color: #ffffff;
box-shadow: 0 1px 4px rgba(0, 0, 0, 0.2);
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.light-theme .subscription-message {
background-color: #6653d9;
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.light-theme .subscription-email {
border-bottom: 1px solid #6653d9;
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color: #f2f2f2;
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.dark-theme .page-header {
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background-image: url("img/rows-dark-checked.svg");
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background-image: url("img/tiles-dark-checked.svg");
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</div></div><div class="js--editor course-editor course-layout__editor course-editor--hidden" id="" data-tab="js" data-split=""><span class="course-editor__label"><span class="course-editor__label-item">JavaScript</span><button class="course-editor__label-item course-editor__label-item--interactive hidden js--editor__unsplit-button course-editor__label-item--simple" title="No split" type="button"><svg width="7" height="10" viewBox="0 0 7 10" xmlns="http://www.w3.org/2000/svg"><g stroke="currentColor" fill="none" fill-rule="evenodd"><path stroke-linecap="round" d="M.6 3.503L3.443.518l2.842 2.985"></path><path d="M3.5 1.5v7.16" stroke-linecap="square"></path></g></svg></button></span><div class="course-editor__item" id="js-editor">// Menu
let menu = document.querySelector('.menu');
menu.onclick = function () {
menu.classList.toggle('menu-open');
menu.classList.toggle('menu-close');
};
// Layuot
let rowViewButton = document.querySelector('.row-view');
let tileViewButton = document.querySelector('.tile-view');
let newsList = document.querySelector('.news-list');
rowViewButton.onclick = function () {
rowViewButton.classList.add('view-checked');
tileViewButton.classList.remove('view-checked');
newsList.classList.remove('list-tiles-view');
};
tileViewButton.onclick = function () {
rowViewButton.classList.remove('view-checked');
tileViewButton.classList.add('view-checked');
newsList.classList.add('list-tiles-view');
};
// Cookies! Om-nom-nom...
let cookies = document.querySelector('.cookies-agreement');
let cookiesButton = document.querySelector('.button');
cookiesButton.onclick = function () {
cookies.classList.add('cookies-agreement-closed');
};
</div></div></div><div class="course-editor-controls"><button class="course-editor-controls__item course-editor-controls__item--answer" type="button">Show the answer</button></div><div class="js--feedback course-unhappy"><button class="js--feedback-btn course-unhappy__button" type="button"><span class="sr-only">Complain</span><svg aria-hidden="true"><use xlink:href="/img/sprites/courses.svg#unhappy"></use></svg></button><div class="js--feedback-modal course-unhappy__modal course-unhappy__modal--step-one"><form method="POST" action="/courses/intro-to-web-development/javascript/javascript/signal" class="course-unhappy__form form"><input type="hidden" name="csrf_name" value="csrf69aebd4c19ae9"><input type="hidden" name="csrf_value" value="cac0978df072b9ec439259aa1b94a329"><p class="course-unhappy__text">What didn’t you like in this task?</p><div class="course-unhappy__slide"><div class="course-unhappy__wrap"><div class="course-unhappy__list"><label class="checkbox checkbox--small"><input class="checkbox__input" name="problems" value="1" type="checkbox"><span class="checkbox__text">The code check doesn’t work</span></label><label class="checkbox checkbox--small"><input class="checkbox__input" name="problems" value="2" type="checkbox"><span class="checkbox__text">The task is too difficult</span></label><label class="checkbox checkbox--small"><input class="checkbox__input" name="problems" value="3" type="checkbox"><span class="checkbox__text">The theory is hard to understand</span></label><label class="checkbox checkbox--small"><input class="js--feedback-other-checkbox checkbox__input" name="problems" value="0" type="checkbox"><span class="checkbox__text">Other (will write below)</span></label></div><div class="course-unhappy__message"><label class="sr-only" for="id-message">Другое (сейчас напишу)</label><textarea class="field field--area" id="id-message" name="message" placeholder="For example, a typo in the word «heading»"></textarea></div></div></div><button class="course-unhappy__control course-unhappy__control--prev" type="button"><span class="sr-only">Prev</span><svg aria-hidden="true"><use xlink:href="/img/sprites/landings.svg#arrow"></use></svg></button><button class="course-unhappy__control course-unhappy__control--next" type="button" disabled><span class="sr-only">Next</span><svg aria-hidden="true"><use xlink:href="/img/sprites/landings.svg#arrow"></use></svg></button><button class="js--submit-btn button" disabled>Submit</button></form><p class="course-unhappy__result hidden">Thanks! We’ll fix everything at once!</p></div></div></div><div class="course-layout__column course-layout__column--right"><span class="course-separator-control"><svg aria-hidden="true"><use xlink:href="/img/sprites/courses.svg#icon-arrows-separator"></use></svg></span><div class="course-browser course-layout__browser"><div class="course-browser__menu"><span class="course-browser__menu-item course-browser__address"><span class="course-browser__menu-item-inner"><span class="course-browser__address-text"></span></span></span><button class="js--autorun course-browser__menu-item course-browser__menu-button course-browser__menu-button--text-with-icon course-browser__menu-button--autorun course-browser__menu-button--autorun-on" title="Autorun" type="button"><span class="course-browser__menu-item-inner"><svg aria-hidden="true"><use xlink:href="/img/sprites/courses.svg#icon-autorun"></use></svg>
Autorun
</span></button><button class="course-browser__menu-item course-browser__menu-button course-browser__menu-button--expand" type="button"><svg xmlns="http://www.w3.org/2000/svg" width="11" height="11" viewBox="0 0 11 11"><path d="M1.375 5.125v4.5h4.5m3.75-3.75v-4.5h-4.5" fill="none" fill-rule="evenodd" stroke="currentColor"></path></svg></button></div><div class="course-browser__content"><div class="course-browser__zoomer"><iframe class="course-browser__zoomer-element js--preview-document"></iframe><p class="course-browser__focus-message">
Click inside the mini browser to put the focus in this window.
</p></div><div class="course-browser__menu course-browser__menu--vertical"><button class="course-browser__menu-item course-browser__menu-button course-browser__menu-button--increase" type="button" disabled title="Larger"><span class="course-browser__menu-item-inner">Larger</span></button><span class="course-browser__menu-item course-browser__zoom"><span class="course-browser__menu-item-inner">100%</span></span><button class="course-browser__menu-item course-browser__menu-button course-browser__menu-button--decrease" type="button" title="Smaller"><span class="course-browser__menu-item-inner">Smaller</span></button></div></div><div class="console console--modal console--modal-collapsed js--console"><div class="console__heading"><span class="console__heading-title">Console<span class="console__counter hidden js--console__counter"></span></span><button class="console__heading-button js--console__toggle" type="button" title="Switch console"><svg aria-hidden="true"><use xlink:href="/img/sprites/courses.svg#icon-collapse"></use></svg></button></div><div class="console__content js--console__content"></div></div><div class="course-goals js--goals"><div class="course-goals__heading"><span class="course-goals__heading-title"><span class="course-goals__count-label">Goals</span><span class="course-goals__count">completed</span></span><div class="js--annotations course-task-stats course-task-stats--disabled course-task-stats--centered "><span class="course-task-stats__indicator"><svg width="12" height="12" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg"><path fill-rule="evenodd" clip-rule="evenodd" d="M15 8C15 11.866 11.866 15 8 15C4.13403 15 1 11.866 1 8C1 4.13403 4.13403 1 8 1C11.866 1 15 4.13403 15 8ZM16 8C16 12.4183 12.4183 16 8 16C3.58173 16 0 12.4183 0 8C0 3.58173 3.58173 0 8 0C12.4183 0 16 3.58173 16 8ZM6.7287 3.88849C6.6958 3.59229 6.92761 3.33325 7.22565 3.33325H8.77502C9.07306 3.33325 9.30487 3.59229 9.27197 3.88849L8.71643 8.88849C8.68829 9.14166 8.47424 9.33325 8.21948 9.33325H7.78119C7.52643 9.33325 7.31238 9.14166 7.28424 8.88849L6.7287 3.88849ZM9.33368 12.0001C9.33368 12.7365 8.73669 13.3334 8.00031 13.3334C7.26392 13.3334 6.66699 12.7365 6.66699 12.0001C6.66699 11.2637 7.26392 10.6667 8.00031 10.6667C8.73669 10.6667 9.33368 11.2637 9.33368 12.0001Z" fill="currentColor"></path></svg><span class="js--annotations-counter course-task-stats__counter">0</span></span><div class="course-task-stats__scroller-wrapper"><div class="course-task-stats__scroller"><ul class="js--annotations-list course-task-stats__list"></ul></div></div></div><button class="course-goals__button course-goals__button--expand js--goals__expand" type="button"><svg aria-hidden="true"><use xlink:href="/img/sprites/courses.svg#icon-collapse"></use></svg></button><a class="course-goals__button course-goals__button--next button button--green button--without-border hidden" href="/courses/intro-to-web-development/javascript/theme-switcher" title="Introduction to the theme switcher"><svg aria-hidden="true"><use xlink:href="/img/sprites/courses.svg#arrow-white--mini"></use></svg></a></div><div class="course-goals__content"><ol class="course-goals__list"><li class="course-goals__list-item">Uncomment the code <code><script src="script.js"></script></code> on line 107. To do this, delete the characters <code><!--</code> and <code>--></code>.</li><li class="course-goals__list-item">In the mini-browser, open the menu by clicking the “hamburger” icon in the upper right corner.</li><li class="course-goals__list-item">In the mini-browser, click the “Tile” button.</li><li class="course-goals__list-item">In the mini-browser, close the cookie warning dialog by clicking the “OK, Continue” button.</li></ol></div></div></div></div></article></div><div class="course-interface__overlay course-interface__overlay--active"></div></main><script
src="https://assets.htmlacademy.org/scripts/courses-spa/htmlacademy-task.v43.js"
data-task-type="html-css-js"
data-assets-path="https://assets.htmlacademy.org/scripts/courses-spa/"
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