JavaScript/Notes/ParameterObject
Passing around lists of parameters? Typechecking arguments? Stop doing that. Here's how to make your code clearer and less error-prone.
The DOM event methods for creating events are an example of what not to do. My comments on w3c DOM mailing list led to the current Event constructor.
Refactoring[edit]
Method initTouchEvent
(Apple) takes 18 parameter variables. It is hard to remember the order and type of each and every variable.
<source lang="javascript">
// Note: This code is iOS specific!
var touchEvent, canceled;
touchEvent = document.createEvent("TouchEvent"); if (typeof touchEvent.initTouchEvent == "function") {
touchEvent.initTouchEvent(type, bubbles, cancelable, view, detail, screenX, screenY, pageX, pageY, ctrlKey, altKey, shiftKey, metaKey, touches, targetTouches, changedTouches, scale, rotation);
// fire the event canceled = target.dispatchEvent(touchEvent);
} </source>
Pass an Object[edit]
It would be much easier can pass in an object that has named property values, and give some defaults for missing property values, such as rotation
.
Like this:
<source lang="javascript">
Action.touchstart( document.body, {clientX: 330, clientY: 330} );
</source>
Where options
has a corresponding property for each argument for a single touch event.
<source lang="javascript"> touchstart : function(target, options) {
return fireTouchEvent("touchstart", target, options);
} </source> <source lang="javascript"> function fireTouchEvent(type, target, options){
var c = getTouchEventData(target, options), doc = target.ownerDocument || target.document || target; //setup default values.
if (!doc || !doc.createTouch) { throw TypeError("simulateTouchEvent(): Invalid target."); }
return simulateTouchEvent(doc, target, type, c.bubbles, c.cancelable, c.view, c.detail, // Not sure what this does in "touch" event. c.screenX, c.screenY, c.pageX, c.pageY, c.ctrlKey, c.altKey, c.shiftKey, c.metaKey, c.touches, c.targetTouches, c.changedTouches, c.scale, c.rotation);
} </source>
Defaults[edit]
<source lang="javascript"> function getTouchEventData(target, options) {
options = options || {}; var doc = target.ownerDocument || target.document || target; return { target : target, bubbles : ("bubbles" in options) ? !!options.bubbles : true, cancelable : ("cancelable" in options) ? !!options.cancelable : true, view : options.view||doc.defaultView, detail : +options.detail||1, // Not sure what this does in "touch" event. screenX : +options.screenX||0, screenY : +options.screenY||0, pageX : +options.pageX||0, pageY : +options.pageY||0, ctrlKey : ("ctrlKey" in options) ? !!options.ctrlKey : false, altKey : ("altKey" in options) ? !!options.altKey : false, shiftKey : ("shiftKey" in options) ? !!options.shiftKey : false, metaKey : ("metaKey" in options) ? !!options.metaKey : false, scale : +options.scale||1, rotation : +options.rotation||0, touches : createTouchList(options.touches||options), targetTouches : createTouchList(options.targetTouches||options), changedTouches: createTouchList(options.changedTouches||options) };
}</source> See also Too Many Parameters.