Does browser fully load js file before execute javascript

The question sounds stupid, but I have this in my mind for period and I want some peace.
Does the browser execute javascript function after a js file is fully loaded, or does it execute immediately after partially loaded.
I ask this because I would design my script architecture accordingly, especially with the new ability of modern browser. Some functions can be executed immediately, and some functions have to execute later.
I'm talking about mufti-thread, asynchronous javascript.
Thank…
Does browser fully load js file before execute javascript

See original post by ketting00