callback-hell.js

findSomething(function(error, something) {  //callback 1
  if (error) {
    throw new Error(error) 
  }
  transformSomething(something, function(error, transformed) { //callback 2
    if (error) {
      throw new Error(error) 
    }
    validateTransformed(transformed, function(error, validated) {  //callback 3
      if (error) {
        throw new Error(error) 
      }
      console.log('data is valid:', validated)
    }) //end 3
  }) //end 2
}) //end 1