docs/lib/mithril.js
function updateEvent(vnode, key2, value) {
		var element = vnode.dom
		var callback = typeof onevent !== "function" ? value : function(e) {
			var result = value.call(element, e)
			onevent.call(element, e)
			return result
		}
		if (key2 in element) element[key2] = typeof value === "function" ? callback : null
		else {
			var eventName = key2.slice(2)
			if (vnode.events === undefined) vnode.events = {}
			if (vnode.events[key2] === callback) return
			if (vnode.events[key2] != null) element.removeEventListener(eventName, vnode.events[key2], false)
			if (typeof value === "function") {
				vnode.events[key2] = callback
				element.addEventListener(eventName, vnode.events[key2], false)
			}
		}
	}
function updateEvent(vnode, key2, value) {
		var element = vnode.dom
		var callback = typeof onevent !== "function" ? value : function(e) {
			var result = value.call(element, e)
			onevent.call(element, e)
			return result
		}
		if (key2 in element) element[key2] = typeof value === "function" ? callback : null
		else {
			var eventName = key2.slice(2)
			if (vnode.events === undefined) vnode.events = {}
			if (vnode.events[key2] === callback) return
			if (vnode.events[key2] != null) element.removeEventListener(eventName, vnode.events[key2], false)
			if (typeof value === "function") {
				vnode.events[key2] = callback
				element.addEventListener(eventName, vnode.events[key2], false)
			}
		}
	}
event