Recently, I came across a fantastic API that promises to simplify working with CANVAS by allowing easy selection and modification of individual elements within the canvas. This API is known as EaselJS, and you can find the documentation here.
While I found the API itself to be quite straightforward, I stumbled upon some JavaScript code that left me puzzled. Specifically, the part enclosed in * * that I couldn't quite decipher. I was curious about the type of JavaScript structure being used here.
(function(target){...content...})(bitmap) and in the content, it references bitmap, which is something outside.
Here is a snippet of the code:
for(var i = 0; i < 100; i++){
bitmap = new Bitmap(image);
container.addChild(bitmap);
bitmap.x = canvas.width * Math.random()|0;
bitmap.y = canvas.height * Math.random()|0;
bitmap.rotation = 360 * Math.random()|0;
bitmap.regX = bitmap.image.width/2|0;
bitmap.regY = bitmap.image.height/2|0;
bitmap.scaleX = bitmap.scaleY = bitmap.scale = Math.random()*0.4+0.6;
bitmap.mouseEnabled = true;
bitmap.name = "bmp_"+i;
(function(target) {
*bitmap.onPress = function(evt) *
{if (window.console && console.log) { console.log("press!"); }
target.scaleX = target.scaleY = target.scale*1.2;
container.addChild(target);
// update the stage while we drag this target
//Ticker provides a central heartbeat for stage to listen to
//At each beat, stage.tick is called and the display list re-rendered
Ticker.addListener(stage);
var offset = {x:target.x-evt.stageX, y:target.y-evt.stageY};
evt.onMouseMove = function(ev) {
target.x = ev.stageX+offset.x;
target.y = ev.stageY+offset.y;
if (window.console && console.log) { console.log("move!"); }
}
evt.onMouseUp = function() {
target.scaleX = target.scaleY = target.scale;
// update the stage one last time to render the scale change, then stop updating:
stage.update();
Ticker.removeListener(stage);
if (window.console && console.log) { console.log("up!"); }
}
** }})(bitmap); **
bitmap.onClick = function() { if (window.console && console.log) { console.log("click!"); } }
}