How to toggle the visibility of division using amp-bind in Google AMP?

Last Updated : 21 Dec, 2020
Introduction: Sometimes you want to add custom interactivity to your AMP pages to make your pages look more user friendly and user calling. Although AMP's pre-built components are limited, so amp-bind is made to overcome this problem. It helps the developer to add custom interactivity to the pages without using AMP's pre-built components.

Setup: To use amp-bind in your page you have to import its script in the header of the document. html 
<script async custom-element="amp-bind" src=
"https://cdn.ampproject.org/v0/amp-bind-0.1.js">
</script>

amp-bind of Google AMP is comprised of three main concepts:

  1. State: State variables are responsible for the update on the page on the basis of user actions. It is very important to define a state variable.
  2. Expression: They are like JavaScript expressions used to refer to the state.
  3. Binding: They are a special attribute that is used to link an element's property to a state via an expression.
Example: Dynamically hiding and showing divisions on the basis of the option selected. html 
<!DOCTYPE html>
<html amp>

<head>
    <meta charset="utf-8" />
    <title>GeeksForGeeks | amp-bind</title>

    <link rel="canonical" href=
"https://amp.dev/documentation/examples/components/amp-bind/index.html" />

    <meta name="viewport" content="width=device-width,
            minimum-scale=1, initial-scale=1" />

    <script async src=
        "https://cdn.ampproject.org/v0.js">
    </script>

    <!-- Import amp-bind component in the header -->
    <script async custom-element="amp-bind" 
        src="https://cdn.ampproject.org/v0/amp-bind-0.1.js">
    </script>

    <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>

    <style amp-custom>
        h1 {
            color: forestgreen;
        }
    </style>
</head>

<body>
    <center>
        <h1>Geeks For Geeks</h1>
    </center>

    <!-- This sample toggles the visibility of 
        two divs based on a input selection. 
        AMP provides the [`hidden` attribute], 
        which we use to hide and show the two 
        divs. Some elements, such as the `select` 
        element, fire [events] we can use to 
        update state -->
    <div style="padding: 1em; color: crimson;">
        <label><u>Select the option</u>: </label>
        <select on="change:AMP.setState
                    ({option: event.value})">
            <option value="0">No selection</option>
            <option value="1">Option 1</option>
            <option value="2">Option 2</option>
        </select>
        <br />

        <div hidden [hidden]="option != 1">
            <h3>You have selected Option 1</h3>
        </div>
        
        <div hidden [hidden]="option != 2">
            <h3>You have selected Option 2</h3>
        </div>
    </div>
</body>

</html>
Output:
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