lib/interface.js
function each(key, interface, fn) {
  var stack = interface.stack;

  for (var i = 0, len = stack.length; i < len; i++) {
    stack[i][key].forEach(fn);
  }
}
function each(key, interface, fn) {
  var stack = interface.stack;

  for (var i = 0, len = stack.length; i < len; i++) {
    stack[i][key].forEach(fn);
  }
}
function each ( key , interface , fn ) { var stack = interface . stack ; for ( var i = 0 , len = stack . length ; i < len ; i ++ ) { stack [ i ] [ key ] . forEach ( fn ) ; } }
Interate through all functions in the stack.

@param {String} key
@param {Interface} interface
@param {Function} fn
@api private
Interate through all functions in the stack .