3.5

205MainStage Effects
Tutorial script 6: Parameter Changed Callback
Print parameter changes to the plug-in console. This example also creates a slider in the
plug-in window and assigns the ParameterChanged function to it.
Text following /* shows comments that explain the JavaScript code.
var PluginParameters = [{name:"Slider", type:"lin", minValue:0, maxValue:1,
numberOfSteps:100, defaultValue:0}];
/* create a slider with a value range of 0.0 to 1.0 and a default value of 0
*/
function ParameterChanged(param, value) {
/* if it is the slider you just created */
if (param == 0) {
Trace(value); /* print the value to the console */
}
}
MainStage Scripter MIDI plug-in Reset function
Reset() is called when you bypass the Scripter plug-in and when the transport is started.
You can implement this function to clear the plug-in history and set Scripter to its default
state.
JavaScript objects overview
The Scripter plug-in provides JavaScript objects that describe or represent MIDI
information and information about MainStage, in addition to performing MIDI processing-
related functions. See these sections for details about different object types.
• Use the JavaScript Event object
• Use the JavaScript TimingInfo object
• Use the Trace object
• Use the MIDI event beatPos property
• Use the JavaScript MIDI object
Use the JavaScript Event object
When the MainStage Scripter MIDI plug-in HandleMIDI function is called, an Event object
represents one MIDI event and implements several methods you can call in your script.
The Event object is not instantiated directly, but is a prototype for the following event-
specific methods, properties, and types.
Tip: You can use the JavaScript “new” keyword to generate a new instance of an Event
object of any type.