Mixin for mithril controllers to enable firebase livedata

firebasemixin.js

/******************************************
 * Firebase mixin
 ******************************************/

export function mixinFirebase(target) {
	var OBJECT = '[object Object]', ARRAY = '[object Array]', STRING = '[object String]', FUNCTION = '[object Function]';
	var type = {}.toString;
	var _references = [];

	function unify(key, value) {
		if(type.call(value) !== OBJECT || !value) {
		    value = { '.value': value };
		}
		value._id = key;
		return value;
	}

	function findIndex(arr, key) {
    	for(var i = 0, l = arr.length; i < l; i++) {
	        if(arr[i]._id === key) {
	            return i;
	        }
	    }
	    return -1;
	}

  	// using the Firebase API's prevChild behavior, we
  	// place each element in the list after it's prev
  	// sibling or, if prevChild is null, at the beginning
  	function positionAfter(arr, prevChild) {
  		var idx;
    	if (prevChild === null) {
        	return 0;
      	} else {
        	idx = findIndex(arr, prevChild);
        	return (idx === -1) ? arr.length: idx + 1;
      	}
	}

	/**
	 * getData - retrieve the data at the specified firebase location once
	 * param @reference firebaseReference - firebase reference to write to
	 * param @oncomplete function - callback function with fetched data
	 * 
	 */
	target.getData = function(reference, oncomplete) {
		reference.once('value', function(snap) {
			oncomplete.call(target, snap.val());
			m.redraw();
		});
	};

	/**
	 * onlivedata - listen to firebase live data changes
	 * param @reference firebaseReference - firebase reference to write to
	 * param @ondata function - callback function with updated data
	 * param @asObject boolean - optional, pass a truthy value to receive a 
	 * 							complete snapshot.val() rather than an array
	 * 
	 */
	target.onlivedata = function(reference, ondata, asObject) {
		// save the reference for later removal of eventlisteners
		_references.push(reference);

		// add eventlistener
		if (asObject) {
			reference.on('value', function(snap) {
				ondata.call(target, snap.val());
				m.redraw();
			});
		} else {
			var out = [];

			reference.on('child_added', function(snap, prevChild) {
				var pos, idx = findIndex(out, snap.key());
				if (idx < 0) {
					pos = positionAfter(out, prevChild);
					out.splice( pos, 0, unify( snap.key(), snap.val() ) );
					ondata.call(target, out);
					m.redraw();
				}
			});

			reference.on('child_changed', function(snap) {
				var idx = findIndex(out, snap.key());
				if (idx > -1) {
					out[idx] = unify( snap.key(), snap.val() );
					ondata.call(target, out);
					m.redraw();
				}
			});

			reference.on('child_removed', function(snap) {
				var idx = findIndex(out,  snap.key());
				out.splice(idx, 1);
				ondata.call(target, out);
				m.redraw();
			});

			reference.on('child_moved', function(snapshot, prevChild) {
				var data, newpos,
					idx = findIndex(out,  snapshot.key());
				if (idx > -1) {
					data = out.splice(idx, 1)[0];
					newpos = positionAfter(out, prevChild);
					out.splice(newpos, 0, data);
					ondata.call(target, out);
					m.redraw();
				}
			});
		}
	};

	/**
	 * bindFirebase - helper function to bind an input value to a firebase location
	 * param @ref firebaseReference - firebase reference to write to
	 * param @key string - key index 
	 * param @property string - key property to bind to
	 * param @attr string - HTML attribute to bind to
	 * return mithril m.withAttr function
	 * 
	 */
	target.bindFirebase = function(reference, key, childProp, attr) {
		return m.withAttr(attr, function(value) {
			reference.child(key).child(childProp).set(value);
		});
	};

	// save a reference to a possible present unload method
	var _savedUnload = (target.onunload)? target.onunload : null;
	
	target.onunload = function() {
		while (_references.length) {
			_references.pop().off();
		}
		_savedUnload && _savedUnload();
	};

	return target;
}


// usage:

var MyCustomers = new Firebase('https://<myfirebase>.firebaseio.com/customers')
var Customers = {};
 
Customers.controller = function(args) {
    var scope = mixinFirebase(this);
    
	scope.onLivedata(args.firebase, function(data) {
		scope.customers = data;
	});
};
 
Customers.view = function(ctrl) {
    return m('ul', ctrl.customers.map(function(customer) {
        return m('li', { key: customer._id }, customer.name );
    }));
};
 
m.module(document.body, Customers, { firebase: MyCustomers });

@kulakowka Would be nice if you'd at least mentioned me as the initial author in your repo's readme or within your license...