amp-bind
Introduction
amp-bind
allows you to add custom interactivity to your pages beyond using AMP's pre-built components.
Setup
Import the amp-bind component in the header.
<script async custom-element="amp-bind" src="https://cdn.ampproject.org/v0/amp-bind-0.1.js"></script>
Basic usage
With amp-bind
, you can update element attributes and values via bindings. Here we update the hidden
attribute based on a state variable called hideGreeting
. On button press, we use the AMP.setState()
action to update the state.
<div hidden [hidden]="hideGreeting">Hello World</div>
<button on="tap:AMP.setState({ hideGreeting: false })">Show greeting</button>
Binding text
You can dynamically change the text value of an element by declaring a binding to the [text]
attribute.
<div>Hello <span [text]="myText">World</span></div>
<button on="tap:AMP.setState({ myText: 'AMP' })">Change text</button>
Binding CSS classes
You can dynamically change the CSS classes of an element by adding a binding to the [class]
attribute.
<div class="background-red" [class]="myClass">Hello World</div>
<button on="tap:AMP.setState({ myClass: 'background-green' })">Change class</button>
Binding width and height
Basic element properties such as width
and height
can be updated as well.
<amp-img src="https://unsplash.it/400/200" width="200" [width]="myImageDimension.width" height="100" [height]="myImageDimension.height">
</amp-img>
<button on="tap:AMP.setState({
myImageDimension: {
width: 400,
height: 200
}
})">
Change size
</button>
Hiding & showing
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.
<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>
<div hidden [hidden]="option != 1">
Option 1
</div>
<div hidden [hidden]="option != 2">
Option 2
</div>
Initializing state
The initial value of an amp-state
variable is null
. However, bindings are not evaluated on page load, but on subsequent user actions. This can lead to unwanted side effects if amp-state
variables are not correctly initialized.
In this sample, both greetings bind to different amp-state
variables. One is initialized via an JSON string inside an amp-state
element, the other is not. When the user triggers an AMP.setState(...)
action, both bindings will be evaluated resulting in the first binding displaying a null
value.
<amp-state id="myInitText"><script type="application/json"> "World" </script></amp-state>
<div>1. Hello <span [text]="undefinedText">World</span></div>
<div>2. Hello <span [text]="myInitText">World</span></div>
<button on="tap:AMP.setState({ myInitText: 'AMP' })">Change state</button>
Push State
AMP.pushState()
writes state changes to the history. Navigating back, will restore the previous state.
To test this, increase the count and use your browser's back button to decrease the count.
<amp-state id="count"><script type="application/json">1</script></amp-state>
<div>Item <span [text]="count">1</span></div>
<button on="tap:AMP.pushState({ count: count + 1 })">Increase count</button>
Debounce input events
For text input, it's a good idea to debounce the input using the input-throttled
event. For a more in-depth example, see autosuggest.
<amp-state id="name"><script type="application/json"> "?" </script></amp-state>
<input id="name-input" placeholder="Enter a name" on="input-throttled:AMP.setState({ name: event.value })">
<div>Hello <span [text]="name">?</span></div>
amp-bind-macro
amp-bind-macro
makes it possible to reuse expressions across different actions.
<amp-bind-macro id="circleArea" arguments="radius" expression="3.14 * radius * radius">
<input type="number" min="0" max="100" value="0" on="input-throttled:AMP.setState({ radius: event.value })">
<div>
The circle has an area of <span [text]="circleArea(radius)">0</span>.
</div>
Si les explications de cette page ne répondent pas à vos questions, n'hésitez pas à contacter d'autres utilisateurs d'AMP pour discuter de votre cas d'utilisation spécifique.
Se rendre sur Stack Overflow Une fonctionnalité n'a pas encore été expliquée ?Le projet AMP encourage fortement votre participation et vos contributions ! Nous espérons que vous deviendrez un membre régulier de notre communauté open source, mais nous serons également ravis de recevoir des contributions ponctuelles concernant les questions qui vous intéressent particulièrement.
Modifier l'exemple sur GitHub-
Written by @choumx