TechQA.

AMP: amp-script is not running

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I am trying to use amp-script to toggle a class on my nav (top menubar) when the window starts to scroll. The effect is to turn the fixed nav from semi-transparent to solid white.

Here is what I tried ...

<!doctype html>
<html ⚡>
<head>
  <meta charset="utf-8">
  <title>My AMP Page</title>
  <link rel="canonical" href="self.html" />
  <meta name="viewport" content="width=device-width,minimum-scale=1,initial-scale=1">
  <style amp-boilerplate>body{-webkit-animation:-amp-start 8s steps(1,end) 0s 1 normal both;-moz-animation:-amp-start 8s steps(1,end) 0s 1 normal both;-ms-animation:-amp-start 8s steps(1,end) 0s 1 normal both;animation:-amp-start 8s steps(1,end) 0s 1 normal both}@-webkit-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-moz-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-ms-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-o-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}</style><noscript><style amp-boilerplate>body{-webkit-animation:none;-moz-animation:none;-ms-animation:none;animation:none}</style></noscript>
  <script async src="https://cdn.ampproject.org/v0.js"></script>
  <script async custom-element="amp-script" src="https://cdn.ampproject.org/v0/amp-script-0.1.js"></script>
  <style amp-custom>
    nav {
      position: fixed;
      top: 0;
      width: 100vw;
      color: white;
      background-color: rgba(0, 0, 0, 0.2);
      z-index: 10;
      text-align: center;
    }

    .opaque {
      background-color: white;
      color: black;
    }

    .hero {
      height: max(25vh, 250px);
      width: 100vw;
      background: red;
    }

    .spacer {
      height: 4em;
      background: blue;
      margin: 0.5em;
    }
  </style>
  <meta name="amp-script-src" content="sha384-bpf6fazoofAb6S1aK0_hOIa1g6nDaC_SPbTuSJsMxEzAPc11oKjAnJZmeFAMKc2p ">
</head>
<body>
  <script id="scroll-listener" type="text/plain" target="amp-script">
    document.addEventListener("scroll", myFunction);

    function myFunction() {
      console.log('scrolled!!');
      if (document.body.scrollTop > 50 || document.documentElement.scrollTop > 50) {
        document.getElementById("topnav").className = "opaque";
      } else {
        document.getElementById("topnav").className = "";
      }
    }
  </script>
  <nav id="topnav">
    <h1>ACME Inc.</h1>
  </nav>
  <main>
    <header class="hero"></header>
    <article>
      <div class="spacer"></div>
      <div class="spacer"></div>
      <div class="spacer"></div>
      <div class="spacer"></div>
      <div class="spacer"></div>
      <div class="spacer"></div>
      <div class="spacer"></div>
      <div class="spacer"></div>
      <div class="spacer"></div>
      <div class="spacer"></div>
      <div class="spacer"></div>
      <div class="spacer"></div>
      <div class="spacer"></div>
      <div class="spacer"></div>
      <div class="spacer"></div>
    </article>
  </main>
</body>
</html>

Unfortunately the script has no effect at all. I've also placed console.log statements to see if I get any scroll events reported at all - and nothing shows up in the console.

Any idea what I'm doing wrong here?

UPDATE: Just to make sure that this works as a "non-AMP" page, I changed the line in the example above:

<script id="scroll-listener" type="text/plain" target="amp-script">...</script>

to this ...

<script id="scroll-listener" type="text/javascript">...</script>

and the site works as expected. So I know for sure that the javascript as written does what I want it to do. The issue is entirely with the way AMP is handling the script.

javascript scroll amp-html
Original Q&A
1

There are 1 answers

4
Alexandr Kazakov On BEST ANSWER

Apparently, you don't understand how amp-script works, which is strange, because there are examples in the official documentation.

Try this example:

<!DOCTYPE html>
<html ⚡>
  <head>
    <meta charset="utf-8" />
    <title>My AMP Page</title>
    <link rel="canonical" href="self.html" />
    <meta name="viewport" content="width=device-width,minimum-scale=1,initial-scale=1" />
    <style amp-boilerplate>
      body {
        -webkit-animation: -amp-start 8s steps(1, end) 0s 1 normal both;
        -moz-animation: -amp-start 8s steps(1, end) 0s 1 normal both;
        -ms-animation: -amp-start 8s steps(1, end) 0s 1 normal both;
        animation: -amp-start 8s steps(1, end) 0s 1 normal both;
      }
      @-webkit-keyframes -amp-start {
        from {
          visibility: hidden;
        }
        to {
          visibility: visible;
        }
      }
      @-moz-keyframes -amp-start {
        from {
          visibility: hidden;
        }
        to {
          visibility: visible;
        }
      }
      @-ms-keyframes -amp-start {
        from {
          visibility: hidden;
        }
        to {
          visibility: visible;
        }
      }
      @-o-keyframes -amp-start {
        from {
          visibility: hidden;
        }
        to {
          visibility: visible;
        }
      }
      @keyframes -amp-start {
        from {
          visibility: hidden;
        }
        to {
          visibility: visible;
        }
      }
    </style>
    <noscript
      ><style amp-boilerplate>
        body {
          -webkit-animation: none;
          -moz-animation: none;
          -ms-animation: none;
          animation: none;
        }
      </style></noscript
    >
    <script async src="https://cdn.ampproject.org/v0.js"></script>
    <script async custom-element="amp-script" src="https://cdn.ampproject.org/v0/amp-script-0.1.js"></script>
    <script async custom-element="amp-bind" src="https://cdn.ampproject.org/v0/amp-bind-0.1.js"></script>
    <meta name="amp-script-src" content="sha384-nPCFvs2yYOVX1DFcHvkEUY1aC6PdG8FAgPUG16rZwxfQJOPh_pM1rA-oUzDsg8pk" />
    <style amp-custom>
      nav {
        position: fixed;
        top: 0;
        width: 100vw;
        color: white;
        background-color: rgba(0, 0, 0, 0.2);
        z-index: 10;
        text-align: center;
      }

      .opaque {
        background-color: white;
        color: black;
      }

      .hero {
        height: max(25vh, 250px);
        width: 100vw;
        background: red;
      }

      .spacer {
        height: 4em;
        background: blue;
        margin: 0.5em;
      }
    </style>
  </head>
  <body>
    <amp-script script="scroll-listener">
      <nav id="topnav">
        <h1>ACME Inc.</h1>
      </nav>
      <main id="main">
        <header class="hero"></header>
        <article>
          <div class="spacer"></div>
          <div class="spacer"></div>
          <div class="spacer"></div>
          <div class="spacer"></div>
          <div class="spacer"></div>
          <div class="spacer"></div>
          <div class="spacer"></div>
          <div class="spacer"></div>
          <div class="spacer"></div>
          <div class="spacer"></div>
          <div class="spacer"></div>
          <div class="spacer"></div>
          <div class="spacer"></div>
          <div class="spacer"></div>
          <div class="spacer"></div>
        </article>
      </main>
    </amp-script>

    <script id="scroll-listener" type="text/plain" target="amp-script">
      function myFunction(event) {
        console.log('scrolled!!');
      }
      window.addEventListener("scroll", myFunction);
    </script>
  </body>
</html>

The example above probably won't help you do what you want, but at least now you'll understand how amp-script works.

amp-script often requires a custom event to be triggered and will not work immediately after the page loads. Read about it here: https://amp.dev/documentation/components/amp-script/?format=websites#user-gestures

To complete this task, I recommend that you use the amp-position-observer and amp-animation components. Here is an example:

<!DOCTYPE html>
<html ⚡>
  <head>
    <meta charset="utf-8" />
    <title>My AMP Page</title>
    <link rel="canonical" href="self.html" />
    <meta name="viewport" content="width=device-width,minimum-scale=1,initial-scale=1" />
    <style amp-boilerplate>
      body {
        -webkit-animation: -amp-start 8s steps(1, end) 0s 1 normal both;
        -moz-animation: -amp-start 8s steps(1, end) 0s 1 normal both;
        -ms-animation: -amp-start 8s steps(1, end) 0s 1 normal both;
        animation: -amp-start 8s steps(1, end) 0s 1 normal both;
      }
      @-webkit-keyframes -amp-start {
        from {
          visibility: hidden;
        }
        to {
          visibility: visible;
        }
      }
      @-moz-keyframes -amp-start {
        from {
          visibility: hidden;
        }
        to {
          visibility: visible;
        }
      }
      @-ms-keyframes -amp-start {
        from {
          visibility: hidden;
        }
        to {
          visibility: visible;
        }
      }
      @-o-keyframes -amp-start {
        from {
          visibility: hidden;
        }
        to {
          visibility: visible;
        }
      }
      @keyframes -amp-start {
        from {
          visibility: hidden;
        }
        to {
          visibility: visible;
        }
      }
    </style>
    <noscript
      ><style amp-boilerplate>
        body {
          -webkit-animation: none;
          -moz-animation: none;
          -ms-animation: none;
          animation: none;
        }
      </style></noscript
    >
    <script async src="https://cdn.ampproject.org/v0.js"></script>
    <script async custom-element="amp-position-observer" src="https://cdn.ampproject.org/v0/amp-position-observer-0.1.js"></script>
    <script async custom-element="amp-animation" src="https://cdn.ampproject.org/v0/amp-animation-0.1.js"></script>

    <style amp-custom>
      nav {
        position: fixed;
        top: 0;
        width: 100vw;
        color: cyan;
        background-color: rgba(0, 0, 0, 0.2);
        z-index: 10;
        text-align: center;
      }

      h1 {
        position: relative;
        z-index: 2;
      }

      .opaque {
        background-color: white;
        color: black;
      }

      .hero {
        height: max(25vh, 250px);
        width: 100vw;
        background: red;
      }

      .spacer {
        height: 4em;
        background: blue;
        margin: 0.5em;
      }

      .scroll-effect {
        background-color: #fff;
        height: 100%;
        left: 0;
        opacity: 0;
        position: absolute;
        top: 0;
        width: 100%;
      }

      .top-anchor {
        position: relative;
      }
    </style>
  </head>
  <body>
    <div class="top-anchor">
      <amp-position-observer on="enter:hideAnim.start; exit:showAnim.start" layout="nodisplay"></amp-position-observer>
    </div>
    <nav id="topnav">
      <span class="scroll-effect" id="scroll-effect"></span>
      <h1>ACME Inc.</h1>
    </nav>
    <main id="main">
      <header class="hero"></header>
      <article>
        <div class="spacer"></div>
        <div class="spacer"></div>
        <div class="spacer"></div>
        <div class="spacer"></div>
        <div class="spacer"></div>
        <div class="spacer"></div>
        <div class="spacer"></div>
        <div class="spacer"></div>
        <div class="spacer"></div>
        <div class="spacer"></div>
        <div class="spacer"></div>
        <div class="spacer"></div>
        <div class="spacer"></div>
        <div class="spacer"></div>
        <div class="spacer"></div>
      </article>
    </main>

    <amp-animation id="showAnim" layout="nodisplay">
      <script type="application/json">
        {
          "duration": "200ms",
          "fill": "both",
          "iterations": "1",
          "direction": "alternate",
          "animations": [
            {
              "selector": "#scroll-effect",
              "keyframes": [
                {
                  "opacity": "1",
                  "visibility": "visible"
                }
              ]
            }
          ]
        }
      </script>
    </amp-animation>
    <amp-animation id="hideAnim" layout="nodisplay">
      <script type="application/json">
        {
          "duration": "200ms",
          "fill": "both",
          "iterations": "1",
          "direction": "alternate",
          "animations": [
            {
              "selector": "#scroll-effect",
              "keyframes": [{ "opacity": "0", "visibility": "hidden" }]
            }
          ]
        }
      </script>
    </amp-animation>
  </body>
</html>

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