jQuery compatibility and enhancement

[liudangyi]

Event System

We are using native JavaScript event now, which brings some trouble when used together with jQuery, such as

// Add an event listener using jQuery
// before
$(form).bind('ajax:success', function(e, data, status, xhr) {
  // code
})
// after
$(form).bind('ajax:success', function(e) {
  var data = e.originalEvent.detail[0]
  var status = e.originalEvent.detail[1]
  var xhr = e.originalEvent.detail[2]
  // code
})

// Manually trigger an event
// before
$(link).trigger('click')
// after
$(link)[0].click()
// before
$(form).trigger('submit')
// after, because el.submit() does't fire the submit event!
if ($(form)[0].dispatchEvent(new Event('submit', { bubbles: true, cancelable: true })) !== false) {
  $(form)[0].submit()
}

There are two helper functions in test/settings.js. However, I'm wondering whether it's acceptable to add these functions to jQuery globally when users import UJS in their projects, or expose them in different APIs.

Ajax (finished)

Old UJS will prefilter all jQuery ajax requests with CSRFProtection header. This behavior shouldn't change in new version.

[gitmihalis]

If the goal is to drop jquery as a dependency, I think it would be better to refrain from using it in testing

[liudangyi]

@gitmihalis Currently I don't much time working on testing it in a real project. But I think it should work smoothly without much modification to existing code.

I've provided a pre-built version of rails.js and if you wish, you can use it to replace the old version, and fire any problems here.