rengokantai / psadvtechjsjq

####psadvtechjsjq #####intro ######1 see canvasv1 no param. ######2 see canvasv2 six param. #######3-7 see respect html file

#####events ######propagation events bubble up the dom until handled

#####using jQuery Deferred Obj ######common pattern christmas tree effect, many indentation ######Deferred object get use deferred, load does not. ######Negative testing. using then(succ,fail) function, if fail multiple times, only return one error
diff of cb and promise. The done and fail methods are registering a handler function with the deferred object. There is nothing to prevent registering multiple handlers for the done and fail methods.(in fact if we save the deferred object as a var, we can attach a handler even afer the object has been resolved or rejected. A cb can only be called once from the original process that received it as a parameter. Assuming we are making a call to jq get , if we pass a cb to that method,it will only get executed once the get method completes. There is no way to expand the func of the callback after is been executed because the get method has completed.

If we ue deferred object that isreturned from the get method instead,we can attach as many done or fail handlers as we wish in any order base on conditional processing. We can even add a handler based on the result of the get.

######Deferred methods defer4-promise.html observe the results

######Dynamic pages ######creating deferred proj The when method return a deferred object.as soon as any of the loadSec return a deferred that is rejected, the enclosing object used by the when method is also rejected, the satte cannot change again ######using when we reject our deferred object, that immediately rejects the deferred object used by the when block