I am new to Web developer field so i want to know advantage and disadvantage of javascript or jquery not coding wise, i expect functionality like it is load very quick, if any browser disable javascript means that time what to do? please explain in detail
You just have to make sure that the content is accessible and usable for users. You can easily test this by turning off JS yourself. A good strategy is to build the page without JS first, and then add the JS functionality on top of that.
Read this (as well as the comments):