[GroSacASacs]

How does this compete with putting a big script tag at the end of the body in the HTML that contains all the code necessary ? What settings can make this way of requiring scripts useful ?

I guess this can be useful, to load extra functionality at run time, in very big single page application.

[jhabdas]

In a large document, or one with scripts embedded throughout, waiting until the body is finished parsing could take considerably longer than async loading in the head.