In a browser, what framework do you use to handle file dependencies? As in I have foo.js which will only run if bar.js is loaded, I don't want to specify in my

In a browser, what framework do you use to handle file dependencies? As in I have foo.js which will only run if bar.js is loaded, I don't want to specify in my page: 1) load bar.js, 2) load foo.js 3) order matters... rather I want to say load foo.js (and implicitly it loads bar.js first)