Advantages

1. Modern browsers are way faster to process JS.
2. Trend – clients are doing what servers used to do
3. Server is used only to generate data like json
4. Client is used only to generate/render html
5. Speed/efficient (no redundant data transfer between server client)

Disadvantage

1. No compile time error checking
2. Once a project becomes big, it is hard to upgrade libraries/framework
   without breaking something (at runtime)
3. Not properly organized (global methods, big script file)

Solution

1. Enclose functions in namespace
2. Modularize code (this way big file can be split)
3. “use strict” (reason)
4. Write unit test (to solve compile time checking)

here is an example -

(function (nsr, $, undefined) {
     "use strict"
     nsr.Module1 = nsr.Module1 || {};
     nsr.Module1.variable1 = 'test';
     nsr.Module1.function1 = function(){}
} (window.nsr = window.nsr || {}, jQuery));