Scripter Javascript Tutorial

60 The if statement

MDN: Control Flow and Error Handling: if...else statement

The if statement is the simplest of all branching. If a specified condition is true, then do something. The if statement has a very simple syntax:

if ( <condition is true> ) {
	<do something>
}

In the above example:

• Line 1: All if statements begin with the reserved word and the condition is contained within parentheses. For the condition to be tested, the comparison, logical, and type operators are used to evaluate whether a condition is true or not.

• Line 2: The code to execute is contained within curly braces on lines 1 and 3

A common example is capturing events passed to HandleMIDI():

function HandleMIDI(event) {
	if (event instanceof NoteOn) {
		Trace(event);
	}
}

In the above example:

• Line 1: Scripter calls the HandleMIDI() function, passing an event.

• Line 2: The if statement evaluates whether the event is an instance of NoteOn.

• Line 3: If the event is NoteOn, then the event is written to the console.

• Line 4: The if statement is closed with the curly brace.

This outputs exactly what would be expected with any MIDI data in the track:

***Creating a new MIDI engine with script***

Evaluating MIDI-processing script...
Script evaluated successfully!
[NoteOn channel:1 pitch:61 [C#3] velocity:100]
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