Javascript Try-Catch Performance Vs. Error Checking Code

“Programs must be written for people
to read, and only incidentally for
machines to execute.”

Abelson & Sussman, SICP, preface to the first edition

Always aim for readable code. The key thing to remember is:

Avoid try-catch in performance-critical functions, and loops

Anywhere else they won’t do much harm. Use them wisely, use them when they make sense.

But as I see you clearly misuse some functions for error checking. You can test for the desired objects and properties of objects right before you use them instead of complex checking. And:

if (YAHOO.lang.isUndefined(projectPhaseId) || YAHOO.lang.isNull(projectPhaseId))

can be written as

if (projectPhaseId != null)

for example… So the example above can be fairly readable even without try catches. You seem to misuse YUI a bit.

I would bet this works as expected:

function getProjectTask(projectTaskId) {

   var projectPhaseId    = projectTaskPhaseMap[projectTaskId],
       projectPhaseIndex = scheduleData.ProjectPhasesMap[projectPhaseId],
       projectPhase      = scheduleData.ProjectPhases[projectPhaseIndex];

  if (projectPhase == null) return null; // projectPhase would break the chain

  var projectTaskIndex  = projectPhase.ProjectTasksMap[projectTaskId],
      projectTask       = scheduleData.ProjectTasks[projectTaskIndex];

   return projectTask || null; // end of the dependency chain

}

How cool is that? 🙂