Web MIDI API
Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.
The Web MIDI API connects to and interacts with Musical Instrument Digital Interface (MIDI) Devices.
The interfaces deal with the practical aspects of sending and receiving MIDI messages. Therefore, the API can be used for musical and non-musical uses, with any MIDI device connected to your computer.
Interfaces
MIDIInputMap
-
Represents all of the available MIDI input ports.
MIDIOutputMap
-
Represents all of the available MIDI output ports.
MIDIAccess
-
Provides the methods to list input and output devices, and to access an individual device.
MIDIPort
-
Represents an individual MIDI port.
MIDIInput
-
Provides a method for dealing with MIDI messages from an input port.
MIDIOutput
-
Queues messages to the linked MIDI port. Messages can be sent immediately or after a specified delay.
MIDIMessageEvent
-
The event passed to
MIDIInput.midimessage_event
. MIDIConnectionEvent
-
The event passed to the
MIDIAccess.statechange_event
andMIDIPort.statechange_event
events, when a port becomes available or unavailable.
Examples
Gaining access to the MIDI port
The navigator.requestMIDIAccess()
method returns a promise that resolves to a MIDIAccess
, which can then be used to access a MIDI device.
The method must be called in a secure context.
var midi = null; // global MIDIAccess object
function onMIDISuccess( midiAccess ) {
console.log( "MIDI ready!" );
midi = midiAccess; // store in the global (in real usage, would probably keep in an object instance)
}
function onMIDIFailure(msg) {
console.log( "Failed to get MIDI access - " + msg );
}
navigator.requestMIDIAccess().then( onMIDISuccess, onMIDIFailure );
Listing inputs and outputs
In this example the list of input and output ports are retrieved and printed to the console.
function listInputsAndOutputs( midiAccess ) {
for (var entry of midiAccess.inputs) {
var input = entry[1];
console.log( "Input port [type:'" + input.type + "'] id:'" + input.id +
"' manufacturer:'" + input.manufacturer + "' name:'" + input.name +
"' version:'" + input.version + "'" );
}
for (var entry of midiAccess.outputs) {
var output = entry[1];
console.log( "Output port [type:'" + output.type + "'] id:'" + output.id +
"' manufacturer:'" + output.manufacturer + "' name:'" + output.name +
"' version:'" + output.version + "'" );
}
}
Handling MIDI Input
This example prints incoming MIDI messages on a single port to the console.
function onMIDIMessage( event ) {
var str = "MIDI message received at timestamp " + event.timeStamp + "[" + event.data.length + " bytes]: ";
for (var i=0; i<event.data.length; i++) {
str += "0x" + event.data[i].toString(16) + " ";
}
console.log( str );
}
function startLoggingMIDIInput( midiAccess, indexOfPort ) {
midiAccess.inputs.forEach( function(entry) {entry.onmidimessage = onMIDIMessage;});
}
Specifications
Specification |
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Web MIDI API |