Most of the time, Firefox, Safari and Opera work without much effort and differences between the 3. However, throw IE into the mix and you’re in a whole different world.This is helpful if you need to dynamically inject javascript.And, the biggest problem was setting a function that you want executed after the script is loaded.By this article I will provide 4 way to dynamically load external JavaScript.
The below 1,2,3 are asynchronous,only 4 is synchronization.