I don't understand.

WTF.js

// This doesn't work:
> var data = $.ajax({ url : '/plans.json'}).responseText
> undefined

// However, if I set data then ask for the responseText, it does. I don't understand why this happens, but I accept it.
> var data = $.ajax({ url : '/plans.json'})
> undefined
> data.responseText
> "[{"plan":{"created_at":"2011-02-21T00:36:29Z","id":1,"updated_at":"2011-02-21T00:36:29Z"}},{"plan":{"created_at":"2011-02- etc etc......


// However, I don't understand why the following the following code doesn't work at all.
> var d = $.ajax({ url : '/plans.json'})
  var data = d.responseText
  console.log(d)
  console.log(d.responseText)  
  console.log(data)

> Object
  undefined
  undefined
  undefined