[js] DOMContentLoad , load event

detect loading [1]

1. DOMContentLoad
   fired by : document object
   when : as soon as the page DOM has been loaded, without waiting for resources to finish loading.
2. load
   fired by : window object
   when : when the whole page has loaded, including all dependent resources such as stylesheets and images.

Refereneces

[1] Window: load event - Mozilla