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x-data

Everything in Alpine starts with the x-data directive.

x-data defines a chunk of HTML as an Alpine component and provides the reactive data for that component to reference.

Here's an example of a contrived dropdown component:

<div x-data="{ open: false }">
    <button @click="open = ! open">Toggle Content</button>

    <div x-show="open">
        Content...
    </div>
</div>

Don't worry about the other directives in this example (@click and x-show), we'll get to those in a bit. For now, let's focus on x-data.

Scope

Properties defined in an x-data directive are available to all element children. Even ones inside other, nested x-data components.

For example:

<div x-data="{ foo: 'bar' }">
    <span x-text="foo"><!-- Will output: "bar" --></span>

    <div x-data="{ bar: 'baz' }">
        <span x-text="foo"><!-- Will output: "bar" --></span>

        <div x-data="{ foo: 'bob' }">
            <span x-text="foo"><!-- Will output: "bob" --></span>
        </div>
    </div>
</div>

Methods

Because x-data is evaluated as a normal JavaScript object, in addition to state, you can store methods and even getters.

For example, let's extract the "Toggle Content" behavior into a method on x-data.

<div x-data="{ open: false, toggle() { this.open = ! this.open } }">
    <button @click="toggle()">Toggle Content</button>

    <div x-show="open">
        Content...
    </div>
</div>

Notice the added toggle() { this.open = ! this.open } method on x-data. This method can now be called from anywhere inside the component.

You'll also notice the usage of this. to access state on the object itself. This is because Alpine evaluates this data object like any standard JavaScript object with a this context.

If you prefer, you can leave the calling parenthesis off of the toggle method completely. For example:

<!-- Before -->
<button @click="toggle()">...</button>

<!-- After -->
<button @click="toggle">...</button>

Getters

JavaScript getters are handy when the sole purpose of a method is to return data based on other state.

Think of them like "computed properties" (although, they are not cached like Vue's computed properties).

Let's refactor our component to use a getter called isOpen instead of accessing open directly.

<div x-data="{
  open: false,
  get isOpen() { return this.open },
  toggle() { this.open = ! this.open },
}">
    <button @click="toggle()">Toggle Content</button>

    <div x-show="isOpen">
        Content...
    </div>
</div>

Notice the "Content" now depends on the isOpen getter instead of the open property directly.

In this case there is no tangible benefit. But in some cases, getters are helpful for providing a more expressive syntax in your components.

Data-less components

Occasionally, you want to create an Alpine component, but you don't need any data.

In these cases, you can always pass in an empty object.

<div x-data="{}"...

However, if you wish, you can also eliminate the attribute value entirely if it looks better to you.

<div x-data...

Single-element components

Sometimes you may only have a single element inside your Alpine component, like the following:

<div x-data="{ open: true }">
    <button @click="open = false" x-show="open">Hide Me</button>
</div>

In these cases, you can declare x-data directly on that single element:

<button x-data="{ open: true }" @click="open = false" x-show="open">
    Hide Me
</button>

Re-usable Data

If you find yourself duplicating the contents of x-data, or you find the inline syntax verbose, you can extract the x-data object out to a dedicated component using Alpine.data.

Here's a quick example:

<div x-data="dropdown">
    <button @click="toggle">Toggle Content</button>

    <div x-show="open">
        Content...
    </div>
</div>

<script>
    document.addEventListener('alpine:init', () => {
        Alpine.data('dropdown', () => ({
            open: false,

            toggle() {
                this.open = ! this.open
            },
        }))
    })
</script>

→ Read more about Alpine.data(...)