Coding standard - apply JSDOC annotation

[tuandm]

I think it's good to apply http://usejsdoc.org/ - not all of them just some basic types.
JSDOC will help IDE and other 3rd parties render/analyze the code base better.

I will start adding some docblocks on js files such as utils/store... if you think it's worth.

[PanJiaChen]

LFTM 👍