Function optimizeCb

underscore-node-f.cjs:738–755

(func, context, argCount)

// of the passed-in callback, to be repeatedly applied in other Underscore
// functions.
function optimizeCb(func, context, argCount) {
  if (context === void 0) return func;
  switch (argCount == null ? 3 : argCount) {
    case 1: return function(value) {
      return func.call(context, value);
    };
    // The 2-argument case is omitted because we’re not using it.
    case 3: return function(value, index, collection) {
      return func.call(context, value, index, collection);
    };
    case 4: return function(accumulator, value, index, collection) {
      return func.call(context, accumulator, value, index, collection);
    };
  }
  return function() {
    return func.apply(context, arguments);
  };
}

// An internal function to generate callbacks that can be applied to each
// element in a collection, returning the desired result — either `_.identity`,