foop/src/deps/loop/traverse/withCyclicalCheck.js

interfaces that describe their intentions.

// https://github.com/andrewplummer/Sugar/blob/master/lib/common.js#L766
function iterateWithCyclicCheck(obj, sortedKeys, stack, fn) {
  function next(val, key) {
    var cyc = false

    // Allowing a step into the structure before triggering this check to save
    // cycles on standard JSON structures and also to try as hard as possible to
    // catch basic properties that may have been modified.
    if (stack.length > 1) {
      var i = stack.length
      while (i--) {
        if (stack[i] === val) {
          cyc = true
        }
      }
    }

    stack.push(val)
    fn(key, val, cyc, stack)
    stack.pop()
  }

  function iterateWithSortedKeys() {
    // Sorted keys is required for serialization, where object order
    // does not matter but stringified order does.
    var arr = getKeys(obj).sort(), key
    for (var i = 0; i < arr.length; i++) {
      key = arr[i]
      next(obj[key], arr[i])
    }
  }

  // This method for checking for cyclic structures was egregiously stolen from
  // the ingenious method by @kitcambridge from the Underscore script:
  // https://github.com/documentcloud/underscore/issues/240
  if (!stack) {
    stack = []
  }

  if (sortedKeys) {
    iterateWithSortedKeys()
  }
  else {
    forEachProperty(obj, next)
  }
}