function getContent(key) {
    var filePath = path.join(__dirname, '../test.txt');
    fs.readFile(filePath, 'utf8', function (err, data) {
        if (err) {
            return console.log(err);
        }
        ....
        var fileKeyValObj = {};
        return fileKeyValObj[key];
    });
}

getContent('web', function (cmd) {
    if (typeof cmd !== 'undefined') {