Example of how to share JavaScript between client and node.js

common.js

function(exports) {

    if(!exports) {
        // This is client side code

        window.MyApp = window.MyApp = window.MyApp || {};
        exports = window.MyApp.common = window.MyApp.common || {}
    }

    exports.foo = function() { 
        return 'bar';
    };

})((typeof process === 'undefined') || !process.versions ? null : exports);