GIT - How to get just one file from another branch

URL: http://stackoverflow.com/questions/2364147/how-to-get-just-one-file-from-another-branch
I am using git and working on master branch. This branch has a file called app.js .
I have an experiment branch in which I made a bunch of changes and tons of commit. Now I want to bring all the changes done only to app.js from experiment to master branch.