the optimize callback method in underscore.js

optimizeCb.js

function optimizeCb(func, context, argCount) {
  if (!context) return func
  
  switch (argCount ? argCount : 3) {
    case 1: return function(val) {
      return func.call(context, val)
    }
    case 2: return function(val, other) {
      return func.call(context, val, other)
    }
    case 3: return function(item, index, collection) {
      return func.call(context, item, index, collection)
    }
    case 4: return function(accu, curr, index, collection) {
      return func.call(context, accu, curr, index, collection)
    }
  }

  return function() {
    return func.apply(context, arguments)
  }
}