Navigator: requestMIDIAccess() method
Limited availability
This feature is not Baseline because it does not work in some of the most widely-used browsers.
Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.
The requestMIDIAccess() method of the Navigator interface returns a Promise representing a request for access to MIDI devices on a user's system. This method is part of the Web MIDI API, which provides a means for accessing, enumerating, and manipulating MIDI devices.
This method may prompt the user for access to MIDI devices available to their system, or it may use a previously established preference to grant or deny access. If permission is granted then the Promise resolves and a MIDIAccess object is returned.
Syntax
requestMIDIAccess() requestMIDIAccess(MIDIOptions) Parameters
MIDIOptionsOptional-
An
Objectrepresenting options to pass into the method. These options are:
Return value
A Promise that resolves with a MIDIAccess object.
Exceptions
AbortErrorDOMException-
Thrown if the document or page is closed due to user navigation.
InvalidStateErrorDOMException-
Thrown if the underlying system raises any errors.
NotSupportedErrorDOMException-
Thrown if the feature or options are not supported by the system.
NotAllowedErrorDOMException-
Thrown if the user or system denies the application from creating a MIDIAccess object with the requested options, or if the document is not allowed to use the feature (for example, because of a Permission Policy, or because the user previously denied a permission request).
Security requirements
Access to the API is subject to the following constraints:
- The method must be called in a secure context.
- Access may be gated by the
midiHTTP Permission Policy. - The user must explicitly grant permission to use the API though a user-agent specific mechanism, or have previously granted permission. Note that if access is denied by a permission policy it cannot be granted by a user permission.
The permission status can be queried using the Permissions API method navigator.permissions.query(), passing a permission descriptor with the midi permission and (optional) sysex property:
navigator.permissions.query({ name: "midi", sysex: true }).then((result) => { if (result.state === "granted") { // Access granted. } else if (result.state === "prompt") { // Using API will prompt for permission } // Permission was denied by user prompt or permission policy }); Examples
Request MIDI access
In the following example, the Navigator.requestMIDIAccess() method returns the MIDIAccess object, which gives access to information about the input and output MIDI ports.
navigator.requestMIDIAccess().then((access) => { // Get lists of available MIDI controllers const inputs = access.inputs.values(); const outputs = access.outputs.values(); // … }); Specifications
| Specification |
|---|
| Web MIDI API # dom-navigator-requestmidiaccess |