chainWrapper.js

    /*
     * A small wrapper to turn a prototype, callback object
     * to a chainable api using promises.
     *
     * Usage:
     * var Klass = function() {}
     * Klass.prototype.log = function(msg, cb) {
     *  console.log(msg);
     *  cb();
     * }
     *
     * chainWrapper(Klass);
     */
    const chainWrapper = function(klass) {
      const promisify = function(fn) {
        return function() {
          return new Promise(function(resolve, reject) {
            fn(function(err, res) {
              return err ? reject(err) : resolve(res);
            });
          })
        }
      }

      let next = new Promise(function(r) { r(); })
      const wrap = function(name) {
        const oldFn = klass.prototype[name];

        klass.prototype[name] = function() {
          next = next.then(promisify(oldFn))
          return this;
        }
      }

      Object.keys(klass.prototype).forEach(wrap);
    }