Scripter Javascript Tutorial

68 Looping through Objects

Looping through the properties of an object is similar to that as with array, except with looping through the keys of the object instead of indexes:

function HandleMIDI(event) {
	var keys = Object.keys(event);
	var length = keys.length;
	for ( var thisKey = 0; thisKey < length; thisKey++ ) {
		var key = keys[thisKey];
		var value = event[key];
		Trace( key + ":" + value );
	}
}

In the above example:

• Line 1: Scripter executes the HandleMIDI() function whenever a new event is encountered. The event is an Object with keys used to get their values.

• Line 2: The Object.keys() function is called to get an array of all the object’s keys.

• Line 3: The length of the keys array is captured.

• Line 4: The for statement is declared.

  • var thisKey = 0 declares the loop’s variable. The value will be used as the index to get strings from the keys array.

  • thisKey < length is the condition to be tested. When the index is less than the length, the code block is executed. When the condition is false—thisKey equals length—–the loop is immediately stopped.

  • thisKey++ will add 1 the value of thisKey after the code block has been executed.