Detect shake gestures in Cordova (Phonegap).

shake.js

/*
The only required option is the "success" callback. Usage:

var shake = new Shake({
	frequency: 300,                                                //milliseconds between polls for accelerometer data.
	waitBetweenShakes: 1000,                                       //milliseconds to wait before watching for more shake events.
	threshold: 12,                                                 //how hard the shake has to be to register.
	success: function(magnitude, accelerationDelta, timestamp) {}, //callback when shake is detected. "this" will be the "shake" object.
	failure: function() {},                                        //callback when watching/getting acceleration fails. "this" will be the "shake" object.
});
shake.startWatch();
shake.stopWatch();
*/

function Shake(options) {
	var shake = this,
		watchId = null,
		defaultOptions = {
			frequency: 300,
			waitBetweenShakes: 1000,
			threshold: 12,
			success: undefined,
			failure: undefined
		},
		previousAcceleration;
	for (var p in defaultOptions)
		if (!options.hasOwnProperty(p))
			options[p] = defaultOptions[p];
	
	// Start watching the accelerometer for a shake gesture
	shake.startWatch = function () {
		if (watchId)
			return;
		watchId = navigator.accelerometer.watchAcceleration(getAccelerationSnapshot, handleError, {
			frequency: options.frequency
		});
	};
	
	// Stop watching the accelerometer for a shake gesture
	shake.stopWatch = function () {
		if (!watchId)
			return;
		navigator.accelerometer.clearWatch(watchId);
		watchId = null;
	};
	
	// Gets the current acceleration snapshot from the last accelerometer watch
	function getAccelerationSnapshot() {
		navigator.accelerometer.getCurrentAcceleration(assessCurrentAcceleration, handleError);
	}
	
	// Assess the current acceleration parameters to determine a shake
	function assessCurrentAcceleration(acceleration) {
		if (!previousAcceleration) {
			previousAcceleration = acceleration;
			return;
		}
		var accelerationDelta = {
			x: acceleration.x - previousAcceleration.x,
			y: acceleration.y - previousAcceleration.y,
			z: acceleration.z - previousAcceleration.z
		};
		var magnitude = Math.sqrt(
			Math.pow(accelerationDelta.x, 2) +
			Math.pow(accelerationDelta.y, 2) +
			Math.pow(accelerationDelta.z, 2)
		);
		if (magnitude >= options.threshold) {
			// Shake detected
			if (options.waitBetweenShakes > 0) {
				shake.stopWatch();
				previousAcceleration = undefined;
			}
			options.success.call(shake, magnitude, accelerationDelta, acceleration.timestamp);
			if (options.waitBetweenShakes > 0)
				setTimeout(
					function() {
						shake.startWatch();
					},
					options.waitBetweenShakes
				);
		}
		else
			previousAcceleration = acceleration;
	}

	// Handle errors here
	function handleError() {
		if (options.failure)
			options.failure.call(shake);
	}
};

@dandv Not so. The main issue that prompted me to fork in the first place is still not right. Lee apparently does not know how to get a 3d vector's magnitude. In his code, a move of 6 in dimension x and -6 in dimension y will result in a nett movement of 0. His does not provide any way to use the error handling function without modifying the plugin. It will also fire shake events continuously which is not what I wanted (see my waitBetweenShakes option). It's nice that it's been Cordova-ised, but I wouldn't use it.

Edit: I was wrong about the nett movement bit, but it's still not getting the magnitude correctly. I'm just not a fan of that shake detection logic.