fix: events handling

[cyfung1031]

getEventTarget(xhr)

• only document.createElement('a') was used.
• document.createDocumentFragment() would be a better way to create EventTarget since the creation of HTMLElement is slightly higher than DocumentFragment
• document.createDocumentFragment() is well supported in ES5. (just Opera 10-12 is unknown)
• No functional affect to the current script.

addEventListener and removeEventListener

• removeEventListener was missing, but mentioned in index.d.ts
• WeakMap is used for this particular usage.
• WeakMap in very old browsers might be not supported, in that case, removeEventListener is ignored.
• No functional affect to the current script.

Minor fix in event handler

• changed event.type = args[0]; to event.type = e.type; to avoid memory leakage of array args. the type must be the same as the args[0]. assignment not required.

[cyfung1031]

Combined Distribution Script ajaxhook.js for Testing (PR 119, 120, 121, 122)
https://cdn.jsdelivr.net/gh/cyfung1031/ajax-hook@1ebe48e08108449669290a226e52fc6fbf7ec9ef/dist/ajaxhook.js

[DAHUIAAAAA]

这次改动是要解决丢失 removeListener 的问题？

[cyfung1031]

这次改动是要解决丢失 removeListener 的问题？

之前只做了addEventListener，addEventListener跟removeEventListener是一對的
addEventListener裡面的把真正listen的function改了，一般removeEventListener是除掉不了

雖然很少機會會用removeEventListener，但你猜不到原本網站其他的XHR處理是怎樣，不理的話有機會報錯