Adobe JSXで特定のjsxファイルが存在すれば読み込む ref: http://qiita.com/mazgi/items/439d7dccb10d9b118db4

file0.txt

$ tree
.
├── lib
│   └── lib1.jsx
└── main.jsx

lib1.jsx

var func = function() { alert('function in lib'); }

main.jsx

const SELF = (function(){
    try {app.documents.test()}
    catch(e) {return File(e.fileName)}
})();

var func = function() { alert('function in main'); }

if(new File(SELF.path + '/lib/lib1.jsx').exists) {
    $.evalFile(SELF.path + '/lib/lib1.jsx');
}

func();