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The very basic logic of script tag

I read documentation. Sometimes. When I desperately need answers. It happens all the time. So I read it a lot. :)

When you learn coding through practice, sometimes you learn it upside-down, but the most important thing is that you DO learn it.

Day 10 lesson:

While <script></script> tag is executing, the rest of the HTML page, which goes after it, waits patiently.

The logic behind it is very important. You can’t see or call any DOM elements, which are placed after <script> tag, because they aren’t rendered yet.

You can check this logic at the example webpage here. Note that when you see the JavaScript alert message, there is no image. It loads only after you click ‘OK’. That happens because <img> tag is placed after <script> in the HTML file, and it waits for the </script> to finish executing:

<!DOCTYPE html>
<html>
  <head>
    <meta http-equiv="Content-type" content="text/html; charset=utf-8">
    <meta http-equiv="Content-Security-Policy" content="default-src 'none'; style-src 'unsafe-inline'; img-src data:; connect-src 'self'">
    <title>Site not found &middot; GitHub Pages</title>
    <style type="text/css" media="screen">
      body {
        background-color: #f1f1f1;
        margin: 0;
        font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
      }


  .container { margin: 50px auto 40px auto; width: 600px; text-align: center; }

  a { color: #4183c4; text-decoration: none; }
  a:hover { text-decoration: underline; }

  h1 { width: 800px; position:relative; left: -100px; letter-spacing: -1px; line-height: 60px; font-size: 60px; font-weight: 100; margin: 0px 0 50px 0; text-shadow: 0 1px 0 #fff; }
  p { color: rgba(0, 0, 0, 0.5); margin: 20px 0; line-height: 1.6; }

  ul { list-style: none; margin: 25px 0; padding: 0; }
  li { display: table-cell; font-weight: bold; width: 1%; }

  .logo { display: inline-block; margin-top: 35px; }
  .logo-img-2x { display: none; }
  @media
  only screen and (-webkit-min-device-pixel-ratio: 2),
  only screen and (   min--moz-device-pixel-ratio: 2),
  only screen and (     -o-min-device-pixel-ratio: 2/1),
  only screen and (        min-device-pixel-ratio: 2),
  only screen and (                min-resolution: 192dpi),
  only screen and (                min-resolution: 2dppx) {
    .logo-img-1x { display: none; }
    .logo-img-2x { display: inline-block; }
  }

  #suggestions {
    margin-top: 35px;
    color: #ccc;
  }
  #suggestions a {
    color: #666666;
    font-weight: 200;
    font-size: 14px;
    margin: 0 10px;
  }

&lt;/style&gt;



</head>
  <body>


&lt;div class=&quot;container&quot;&gt;

  &lt;h1&gt;404&lt;/h1&gt;
  &lt;p&gt;&lt;strong&gt;There isn&#39;t a GitHub Pages site here.&lt;/strong&gt;&lt;/p&gt;

  &lt;p&gt;
    If you&#39;re trying to publish one,
    &lt;a href=&quot;https://help.github.com/pages/&quot;&gt;read the full documentation&lt;/a&gt;
    to learn how to set up &lt;strong&gt;GitHub Pages&lt;/strong&gt;
    for your repository, organization, or user account.
  &lt;/p&gt;

  &lt;div id=&quot;suggestions&quot;&gt;
    &lt;a href=&quot;https://githubstatus.com&quot;&gt;GitHub Status&lt;/a&gt; &amp;mdash;
    &lt;a href=&quot;https://twitter.com/githubstatus&quot;&gt;@githubstatus&lt;/a&gt;
  &lt;/div&gt;

  &lt;a href=&quot;/&quot; class=&quot;logo logo-img-1x&quot;&gt;
    &lt;img width=&quot;32&quot; height=&quot;32&quot; title=&quot;&quot; alt=&quot;&quot; src=&quot;data:image/png;base64,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&quot;&gt;
  &lt;/a&gt;

  &lt;a href=&quot;/&quot; class=&quot;logo logo-img-2x&quot;&gt;
    &lt;img width=&quot;32&quot; height=&quot;32&quot; title=&quot;&quot; alt=&quot;&quot; src=&quot;data:image/png;base64,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&quot;&gt;
  &lt;/a&gt;
&lt;/div&gt;



</body>
</html>

Screenshot of the example page:

Amazing photo by Annick Jaquillard

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