ifthen

Facilitate if-then-else-finally structure in asynchronous callbacks

ifthen: support if/then/else/finally branch logic in Javascript callbacks

ifthen.if_(/* condition */)
      .then_(
          // required, called if `condition`  
 
          function (callback) {
              // callback must be called to trigger completion 
              callback();
          })
      .else_(
          // optional; called when `! condition` 
          // cannot be specified unless `then_` is 
 
          function (callback) {
              // callback must be called to trigger completion 
 
              callback();
          })
      .finally_(
          // optional, always called after branch completes 
 
          function (err) {
            // 
          }
      );