sugar/common/internal/iterateWithCyclicCheck.js

A Javascript utility library for working with native objects.

'use strict';

var getKeys = require('./getKeys'),
    coreUtilityAliases = require('../var/coreUtilityAliases');

var forEachProperty = coreUtilityAliases.forEachProperty;

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);
  }
}

module.exports = iterateWithCyclicCheck;