Invoker Commands API

Concepts and usage

A common pattern on the web is to have <button> elements control various aspects of the page, such as opening and closing popovers or <dialog> elements, formatting text, and more.

Historically creating these kinds of controls has required JavaScript event listeners added to the button which can then call the APIs on the element they control. The commandForElement and command properties provide a way to do this declaratively for a limited set of actions. This can be advantageous for built-in commands as the user does not have to wait for JavaScript to download and execute to make these buttons interactive.

HTML attributes

commandfor

Turns a <button> element into a command invoker, controlling the given interactive element; takes the ID of the element to control as its value.

command

Specifies the action to be performed on an element being controlled by a control <button>, specified via the commandfor attribute.

Interfaces

CommandEvent

Represents an event notifying the user that a command has been issued. It is the event object for the command event. The event fires on element referenced by commandForElement.

Extensions to other interfaces

Instance properties

HTMLButtonElement.commandForElement

Gets and sets the element being controlled by the button. The JavaScript equivalent of the commandfor HTML attribute.

HTMLButtonElement.command

Gets and sets the action to be performed on the element being controlled by the button. Reflects the value of the command HTML attribute.

Events

command event

Fired on the element referenced by the button.

Examples

Creating declarative popovers

<button commandfor="mypopover" command="toggle-popover">
  Toggle the popover
</button>
<div id="mypopover" popover>
  <button commandfor="mypopover" command="hide-popover">Close</button>
  Popover content
</div>

Creating declarative dialogs

<button commandfor="mydialog" command="show-modal">Show modal dialog</button>
<dialog id="mydialog">
  <button commandfor="mydialog" command="close">Close</button>
  Dialog Content
</dialog>

Creating custom commands

<button commandfor="my-img" command="--rotate-left">Rotate left</button>
<button commandfor="my-img" command="--rotate-right">Rotate right</button>
<img id="my-img" src="photo.jpg" alt="[add appropriate alt text here]" />

const myImg = document.getElementById("my-img");

myImg.addEventListener("command", (event) => {
  if (event.command === "--rotate-left") {
    myImg.style.rotate = "-90deg";
  } else if (event.command === "--rotate-right") {
    myImg.style.rotate = "90deg";
  }
});

Specifications

Browser compatibility

api.CommandEvent

api.HTMLButtonElement.commandForElement

api.HTMLButtonElement.command

See also

• command property
• commandForElement property
• CommandEvent interface