homework/js/Project/node_modules/history/cjs/history.js

'use strict';

Object.defineProperty(exports, '__esModule', { value: true });

function _interopDefault (ex) { return (ex && (typeof ex === 'object') && 'default' in ex) ? ex['default'] : ex; }

var resolvePathname = _interopDefault(require('resolve-pathname'));
var valueEqual = _interopDefault(require('value-equal'));
var warning = _interopDefault(require('tiny-warning'));
var invariant = _interopDefault(require('tiny-invariant'));

function _extends() {
  _extends = Object.assign || function (target) {
    for (var i = 1; i < arguments.length; i++) {
      var source = arguments[i];

      for (var key in source) {
        if (Object.prototype.hasOwnProperty.call(source, key)) {
          target[key] = source[key];
        }
      }
    }

    return target;
  };

  return _extends.apply(this, arguments);
}

function addLeadingSlash(path) {
  return path.charAt(0) === '/' ? path : '/' + path;
}
function stripLeadingSlash(path) {
  return path.charAt(0) === '/' ? path.substr(1) : path;
}
function hasBasename(path, prefix) {
  return path.toLowerCase().indexOf(prefix.toLowerCase()) === 0 && '/?#'.indexOf(path.charAt(prefix.length)) !== -1;
}
function stripBasename(path, prefix) {
  return hasBasename(path, prefix) ? path.substr(prefix.length) : path;
}
function stripTrailingSlash(path) {
  return path.charAt(path.length - 1) === '/' ? path.slice(0, -1) : path;
}
function parsePath(path) {
  var pathname = path || '/';
  var search = '';
  var hash = '';
  var hashIndex = pathname.indexOf('#');

  if (hashIndex !== -1) {
    hash = pathname.substr(hashIndex);
    pathname = pathname.substr(0, hashIndex);
  }

  var searchIndex = pathname.indexOf('?');

  if (searchIndex !== -1) {
    search = pathname.substr(searchIndex);
    pathname = pathname.substr(0, searchIndex);
  }

  return {
    pathname: pathname,
    search: search === '?' ? '' : search,
    hash: hash === '#' ? '' : hash
  };
}
function createPath(location) {
  var pathname = location.pathname,
      search = location.search,
      hash = location.hash;
  var path = pathname || '/';
  if (search && search !== '?') path += search.charAt(0) === '?' ? search : "?" + search;
  if (hash && hash !== '#') path += hash.charAt(0) === '#' ? hash : "#" + hash;
  return path;
}

function createLocation(path, state, key, currentLocation) {
  var location;

  if (typeof path === 'string') {
    // Two-arg form: push(path, state)
    location = parsePath(path);
    location.state = state;
  } else {
    // One-arg form: push(location)
    location = _extends({}, path);
    if (location.pathname === undefined) location.pathname = '';

    if (location.search) {
      if (location.search.charAt(0) !== '?') location.search = '?' + location.search;
    } else {
      location.search = '';
    }

    if (location.hash) {
      if (location.hash.charAt(0) !== '#') location.hash = '#' + location.hash;
    } else {
      location.hash = '';
    }

    if (state !== undefined && location.state === undefined) location.state = state;
  }

  try {
    location.pathname = decodeURI(location.pathname);
  } catch (e) {
    if (e instanceof URIError) {
      throw new URIError('Pathname "' + location.pathname + '" could not be decoded. ' + 'This is likely caused by an invalid percent-encoding.');
    } else {
      throw e;
    }
  }

  if (key) location.key = key;

  if (currentLocation) {
    // Resolve incomplete/relative pathname relative to current location.
    if (!location.pathname) {
      location.pathname = currentLocation.pathname;
    } else if (location.pathname.charAt(0) !== '/') {
      location.pathname = resolvePathname(location.pathname, currentLocation.pathname);
    }
  } else {
    // When there is no prior location and pathname is empty, set it to /
    if (!location.pathname) {
      location.pathname = '/';
    }
  }

  return location;
}
function locationsAreEqual(a, b) {
  return a.pathname === b.pathname && a.search === b.search && a.hash === b.hash && a.key === b.key && valueEqual(a.state, b.state);
}

function createTransitionManager() {
  var prompt = null;

  function setPrompt(nextPrompt) {
    warning(prompt == null, 'A history supports only one prompt at a time');
    prompt = nextPrompt;
    return function () {
      if (prompt === nextPrompt) prompt = null;
    };
  }

  function confirmTransitionTo(location, action, getUserConfirmation, callback) {
    // TODO: If another transition starts while we're still confirming
    // the previous one, we may end up in a weird state. Figure out the
    // best way to handle this.
    if (prompt != null) {
      var result = typeof prompt === 'function' ? prompt(location, action) : prompt;

      if (typeof result === 'string') {
        if (typeof getUserConfirmation === 'function') {
          getUserConfirmation(result, callback);
        } else {
          warning(false, 'A history needs a getUserConfirmation function in order to use a prompt message');
          callback(true);
        }
      } else {
        // Return false from a transition hook to cancel the transition.
        callback(result !== false);
      }
    } else {
      callback(true);
    }
  }

  var listeners = [];

  function appendListener(fn) {
    var isActive = true;

    function listener() {
      if (isActive) fn.apply(void 0, arguments);
    }

    listeners.push(listener);
    return function () {
      isActive = false;
      listeners = listeners.filter(function (item) {
        return item !== listener;
      });
    };
  }

  function notifyListeners() {
    for (var _len = arguments.length, args = new Array(_len), _key = 0; _key < _len; _key++) {
      args[_key] = arguments[_key];
    }

    listeners.forEach(function (listener) {
      return listener.apply(void 0, args);
    });
  }

  return {
    setPrompt: setPrompt,
    confirmTransitionTo: confirmTransitionTo,
    appendListener: appendListener,
    notifyListeners: notifyListeners
  };
}

var canUseDOM = !!(typeof window !== 'undefined' && window.document && window.document.createElement);
function getConfirmation(message, callback) {
  callback(window.confirm(message)); // eslint-disable-line no-alert
}
/**
 * Returns true if the HTML5 history API is supported. Taken from Modernizr.
 *
 * https://github.com/Modernizr/Modernizr/blob/master/LICENSE
 * https://github.com/Modernizr/Modernizr/blob/master/feature-detects/history.js
 * changed to avoid false negatives for Windows Phones: https://github.com/reactjs/react-router/issues/586
 */

function supportsHistory() {
  var ua = window.navigator.userAgent;
  if ((ua.indexOf('Android 2.') !== -1 || ua.indexOf('Android 4.0') !== -1) && ua.indexOf('Mobile Safari') !== -1 && ua.indexOf('Chrome') === -1 && ua.indexOf('Windows Phone') === -1) return false;
  return window.history && 'pushState' in window.history;
}
/**
 * Returns true if browser fires popstate on hash change.
 * IE10 and IE11 do not.
 */

function supportsPopStateOnHashChange() {
  return window.navigator.userAgent.indexOf('Trident') === -1;
}
/**
 * Returns false if using go(n) with hash history causes a full page reload.
 */

function supportsGoWithoutReloadUsingHash() {
  return window.navigator.userAgent.indexOf('Firefox') === -1;
}
/**
 * Returns true if a given popstate event is an extraneous WebKit event.
 * Accounts for the fact that Chrome on iOS fires real popstate events
 * containing undefined state when pressing the back button.
 */

function isExtraneousPopstateEvent(event) {
  return event.state === undefined && navigator.userAgent.indexOf('CriOS') === -1;
}

var PopStateEvent = 'popstate';
var HashChangeEvent = 'hashchange';

function getHistoryState() {
  try {
    return window.history.state || {};
  } catch (e) {
    // IE 11 sometimes throws when accessing window.history.state
    // See https://github.com/ReactTraining/history/pull/289
    return {};
  }
}
/**
 * Creates a history object that uses the HTML5 history API including
 * pushState, replaceState, and the popstate event.
 */


function createBrowserHistory(props) {
  if (props === void 0) {
    props = {};
  }

  !canUseDOM ? invariant(false, 'Browser history needs a DOM') : void 0;
  var globalHistory = window.history;
  var canUseHistory = supportsHistory();
  var needsHashChangeListener = !supportsPopStateOnHashChange();
  var _props = props,
      _props$forceRefresh = _props.forceRefresh,
      forceRefresh = _props$forceRefresh === void 0 ? false : _props$forceRefresh,
      _props$getUserConfirm = _props.getUserConfirmation,
      getUserConfirmation = _props$getUserConfirm === void 0 ? getConfirmation : _props$getUserConfirm,
      _props$keyLength = _props.keyLength,
      keyLength = _props$keyLength === void 0 ? 6 : _props$keyLength;
  var basename = props.basename ? stripTrailingSlash(addLeadingSlash(props.basename)) : '';

  function getDOMLocation(historyState) {
    var _ref = historyState || {},
        key = _ref.key,
        state = _ref.state;

    var _window$location = window.location,
        pathname = _window$location.pathname,
        search = _window$location.search,
        hash = _window$location.hash;
    var path = pathname + search + hash;
    warning(!basename || hasBasename(path, basename), 'You are attempting to use a basename on a page whose URL path does not begin ' + 'with the basename. Expected path "' + path + '" to begin with "' + basename + '".');
    if (basename) path = stripBasename(path, basename);
    return createLocation(path, state, key);
  }

  function createKey() {
    return Math.random().toString(36).substr(2, keyLength);
  }

  var transitionManager = createTransitionManager();

  function setState(nextState) {
    _extends(history, nextState);

    history.length = globalHistory.length;
    transitionManager.notifyListeners(history.location, history.action);
  }

  function handlePopState(event) {
    // Ignore extraneous popstate events in WebKit.
    if (isExtraneousPopstateEvent(event)) return;
    handlePop(getDOMLocation(event.state));
  }

  function handleHashChange() {
    handlePop(getDOMLocation(getHistoryState()));
  }

  var forceNextPop = false;

  function handlePop(location) {
    if (forceNextPop) {
      forceNextPop = false;
      setState();
    } else {
      var action = 'POP';
      transitionManager.confirmTransitionTo(location, action, getUserConfirmation, function (ok) {
        if (ok) {
          setState({
            action: action,
            location: location
          });
        } else {
          revertPop(location);
        }
      });
    }
  }

  function revertPop(fromLocation) {
    var toLocation = history.location; // TODO: We could probably make this more reliable by
    // keeping a list of keys we've seen in sessionStorage.
    // Instead, we just default to 0 for keys we don't know.

    var toIndex = allKeys.indexOf(toLocation.key);
    if (toIndex === -1) toIndex = 0;
    var fromIndex = allKeys.indexOf(fromLocation.key);
    if (fromIndex === -1) fromIndex = 0;
    var delta = toIndex - fromIndex;

    if (delta) {
      forceNextPop = true;
      go(delta);
    }
  }

  var initialLocation = getDOMLocation(getHistoryState());
  var allKeys = [initialLocation.key]; // Public interface

  function createHref(location) {
    return basename + createPath(location);
  }

  function push(path, state) {
    warning(!(typeof path === 'object' && path.state !== undefined && state !== undefined), 'You should avoid providing a 2nd state argument to push when the 1st ' + 'argument is a location-like object that already has state; it is ignored');
    var action = 'PUSH';
    var location = createLocation(path, state, createKey(), history.location);
    transitionManager.confirmTransitionTo(location, action, getUserConfirmation, function (ok) {
      if (!ok) return;
      var href = createHref(location);
      var key = location.key,
          state = location.state;

      if (canUseHistory) {
        globalHistory.pushState({
          key: key,
          state: state
        }, null, href);

        if (forceRefresh) {
          window.location.href = href;
        } else {
          var prevIndex = allKeys.indexOf(history.location.key);
          var nextKeys = allKeys.slice(0, prevIndex + 1);
          nextKeys.push(location.key);
          allKeys = nextKeys;
          setState({
            action: action,
            location: location
          });
        }
      } else {
        warning(state === undefined, 'Browser history cannot push state in browsers that do not support HTML5 history');
        window.location.href = href;
      }
    });
  }

  function replace(path, state) {
    warning(!(typeof path === 'object' && path.state !== undefined && state !== undefined), 'You should avoid providing a 2nd state argument to replace when the 1st ' + 'argument is a location-like object that already has state; it is ignored');
    var action = 'REPLACE';
    var location = createLocation(path, state, createKey(), history.location);
    transitionManager.confirmTransitionTo(location, action, getUserConfirmation, function (ok) {
      if (!ok) return;
      var href = createHref(location);
      var key = location.key,
          state = location.state;

      if (canUseHistory) {
        globalHistory.replaceState({
          key: key,
          state: state
        }, null, href);

        if (forceRefresh) {
          window.location.replace(href);
        } else {
          var prevIndex = allKeys.indexOf(history.location.key);
          if (prevIndex !== -1) allKeys[prevIndex] = location.key;
          setState({
            action: action,
            location: location
          });
        }
      } else {
        warning(state === undefined, 'Browser history cannot replace state in browsers that do not support HTML5 history');
        window.location.replace(href);
      }
    });
  }

  function go(n) {
    globalHistory.go(n);
  }

  function goBack() {
    go(-1);
  }

  function goForward() {
    go(1);
  }

  var listenerCount = 0;

  function checkDOMListeners(delta) {
    listenerCount += delta;

    if (listenerCount === 1 && delta === 1) {
      window.addEventListener(PopStateEvent, handlePopState);
      if (needsHashChangeListener) window.addEventListener(HashChangeEvent, handleHashChange);
    } else if (listenerCount === 0) {
      window.removeEventListener(PopStateEvent, handlePopState);
      if (needsHashChangeListener) window.removeEventListener(HashChangeEvent, handleHashChange);
    }
  }

  var isBlocked = false;

  function block(prompt) {
    if (prompt === void 0) {
      prompt = false;
    }

    var unblock = transitionManager.setPrompt(prompt);

    if (!isBlocked) {
      checkDOMListeners(1);
      isBlocked = true;
    }

    return function () {
      if (isBlocked) {
        isBlocked = false;
        checkDOMListeners(-1);
      }

      return unblock();
    };
  }

  function listen(listener) {
    var unlisten = transitionManager.appendListener(listener);
    checkDOMListeners(1);
    return function () {
      checkDOMListeners(-1);
      unlisten();
    };
  }

  var history = {
    length: globalHistory.length,
    action: 'POP',
    location: initialLocation,
    createHref: createHref,
    push: push,
    replace: replace,
    go: go,
    goBack: goBack,
    goForward: goForward,
    block: block,
    listen: listen
  };
  return history;
}

var HashChangeEvent$1 = 'hashchange';
var HashPathCoders = {
  hashbang: {
    encodePath: function encodePath(path) {
      return path.charAt(0) === '!' ? path : '!/' + stripLeadingSlash(path);
    },
    decodePath: function decodePath(path) {
      return path.charAt(0) === '!' ? path.substr(1) : path;
    }
  },
  noslash: {
    encodePath: stripLeadingSlash,
    decodePath: addLeadingSlash
  },
  slash: {
    encodePath: addLeadingSlash,
    decodePath: addLeadingSlash
  }
};

function stripHash(url) {
  var hashIndex = url.indexOf('#');
  return hashIndex === -1 ? url : url.slice(0, hashIndex);
}

function getHashPath() {
  // We can't use window.location.hash here because it's not
  // consistent across browsers - Firefox will pre-decode it!
  var href = window.location.href;
  var hashIndex = href.indexOf('#');
  return hashIndex === -1 ? '' : href.substring(hashIndex + 1);
}

function pushHashPath(path) {
  window.location.hash = path;
}

function replaceHashPath(path) {
  window.location.replace(stripHash(window.location.href) + '#' + path);
}

function createHashHistory(props) {
  if (props === void 0) {
    props = {};
  }

  !canUseDOM ? invariant(false, 'Hash history needs a DOM') : void 0;
  var globalHistory = window.history;
  var canGoWithoutReload = supportsGoWithoutReloadUsingHash();
  var _props = props,
      _props$getUserConfirm = _props.getUserConfirmation,
      getUserConfirmation = _props$getUserConfirm === void 0 ? getConfirmation : _props$getUserConfirm,
      _props$hashType = _props.hashType,
      hashType = _props$hashType === void 0 ? 'slash' : _props$hashType;
  var basename = props.basename ? stripTrailingSlash(addLeadingSlash(props.basename)) : '';
  var _HashPathCoders$hashT = HashPathCoders[hashType],
      encodePath = _HashPathCoders$hashT.encodePath,
      decodePath = _HashPathCoders$hashT.decodePath;

  function getDOMLocation() {
    var path = decodePath(getHashPath());
    warning(!basename || hasBasename(path, basename), 'You are attempting to use a basename on a page whose URL path does not begin ' + 'with the basename. Expected path "' + path + '" to begin with "' + basename + '".');
    if (basename) path = stripBasename(path, basename);
    return createLocation(path);
  }

  var transitionManager = createTransitionManager();

  function setState(nextState) {
    _extends(history, nextState);

    history.length = globalHistory.length;
    transitionManager.notifyListeners(history.location, history.action);
  }

  var forceNextPop = false;
  var ignorePath = null;

  function locationsAreEqual$$1(a, b) {
    return a.pathname === b.pathname && a.search === b.search && a.hash === b.hash;
  }

  function handleHashChange() {
    var path = getHashPath();
    var encodedPath = encodePath(path);

    if (path !== encodedPath) {
      // Ensure we always have a properly-encoded hash.
      replaceHashPath(encodedPath);
    } else {
      var location = getDOMLocation();
      var prevLocation = history.location;
      if (!forceNextPop && locationsAreEqual$$1(prevLocation, location)) return; // A hashchange doesn't always == location change.

      if (ignorePath === createPath(location)) return; // Ignore this change; we already setState in push/replace.

      ignorePath = null;
      handlePop(location);
    }
  }

  function handlePop(location) {
    if (forceNextPop) {
      forceNextPop = false;
      setState();
    } else {
      var action = 'POP';
      transitionManager.confirmTransitionTo(location, action, getUserConfirmation, function (ok) {
        if (ok) {
          setState({
            action: action,
            location: location
          });
        } else {
          revertPop(location);
        }
      });
    }
  }

  function revertPop(fromLocation) {
    var toLocation = history.location; // TODO: We could probably make this more reliable by
    // keeping a list of paths we've seen in sessionStorage.
    // Instead, we just default to 0 for paths we don't know.

    var toIndex = allPaths.lastIndexOf(createPath(toLocation));
    if (toIndex === -1) toIndex = 0;
    var fromIndex = allPaths.lastIndexOf(createPath(fromLocation));
    if (fromIndex === -1) fromIndex = 0;
    var delta = toIndex - fromIndex;

    if (delta) {
      forceNextPop = true;
      go(delta);
    }
  } // Ensure the hash is encoded properly before doing anything else.


  var path = getHashPath();
  var encodedPath = encodePath(path);
  if (path !== encodedPath) replaceHashPath(encodedPath);
  var initialLocation = getDOMLocation();
  var allPaths = [createPath(initialLocation)]; // Public interface

  function createHref(location) {
    var baseTag = document.querySelector('base');
    var href = '';

    if (baseTag && baseTag.getAttribute('href')) {
      href = stripHash(window.location.href);
    }

    return href + '#' + encodePath(basename + createPath(location));
  }

  function push(path, state) {
    warning(state === undefined, 'Hash history cannot push state; it is ignored');
    var action = 'PUSH';
    var location = createLocation(path, undefined, undefined, history.location);
    transitionManager.confirmTransitionTo(location, action, getUserConfirmation, function (ok) {
      if (!ok) return;
      var path = createPath(location);
      var encodedPath = encodePath(basename + path);
      var hashChanged = getHashPath() !== encodedPath;

      if (hashChanged) {
        // We cannot tell if a hashchange was caused by a PUSH, so we'd
        // rather setState here and ignore the hashchange. The caveat here
        // is that other hash histories in the page will consider it a POP.
        ignorePath = path;
        pushHashPath(encodedPath);
        var prevIndex = allPaths.lastIndexOf(createPath(history.location));
        var nextPaths = allPaths.slice(0, prevIndex + 1);
        nextPaths.push(path);
        allPaths = nextPaths;
        setState({
          action: action,
          location: location
        });
      } else {
        warning(false, 'Hash history cannot PUSH the same path; a new entry will not be added to the history stack');
        setState();
      }
    });
  }

  function replace(path, state) {
    warning(state === undefined, 'Hash history cannot replace state; it is ignored');
    var action = 'REPLACE';
    var location = createLocation(path, undefined, undefined, history.location);
    transitionManager.confirmTransitionTo(location, action, getUserConfirmation, function (ok) {
      if (!ok) return;
      var path = createPath(location);
      var encodedPath = encodePath(basename + path);
      var hashChanged = getHashPath() !== encodedPath;

      if (hashChanged) {
        // We cannot tell if a hashchange was caused by a REPLACE, so we'd
        // rather setState here and ignore the hashchange. The caveat here
        // is that other hash histories in the page will consider it a POP.
        ignorePath = path;
        replaceHashPath(encodedPath);
      }

      var prevIndex = allPaths.indexOf(createPath(history.location));
      if (prevIndex !== -1) allPaths[prevIndex] = path;
      setState({
        action: action,
        location: location
      });
    });
  }

  function go(n) {
    warning(canGoWithoutReload, 'Hash history go(n) causes a full page reload in this browser');
    globalHistory.go(n);
  }

  function goBack() {
    go(-1);
  }

  function goForward() {
    go(1);
  }

  var listenerCount = 0;

  function checkDOMListeners(delta) {
    listenerCount += delta;

    if (listenerCount === 1 && delta === 1) {
      window.addEventListener(HashChangeEvent$1, handleHashChange);
    } else if (listenerCount === 0) {
      window.removeEventListener(HashChangeEvent$1, handleHashChange);
    }
  }

  var isBlocked = false;

  function block(prompt) {
    if (prompt === void 0) {
      prompt = false;
    }

    var unblock = transitionManager.setPrompt(prompt);

    if (!isBlocked) {
      checkDOMListeners(1);
      isBlocked = true;
    }

    return function () {
      if (isBlocked) {
        isBlocked = false;
        checkDOMListeners(-1);
      }

      return unblock();
    };
  }

  function listen(listener) {
    var unlisten = transitionManager.appendListener(listener);
    checkDOMListeners(1);
    return function () {
      checkDOMListeners(-1);
      unlisten();
    };
  }

  var history = {
    length: globalHistory.length,
    action: 'POP',
    location: initialLocation,
    createHref: createHref,
    push: push,
    replace: replace,
    go: go,
    goBack: goBack,
    goForward: goForward,
    block: block,
    listen: listen
  };
  return history;
}

function clamp(n, lowerBound, upperBound) {
  return Math.min(Math.max(n, lowerBound), upperBound);
}
/**
 * Creates a history object that stores locations in memory.
 */


function createMemoryHistory(props) {
  if (props === void 0) {
    props = {};
  }

  var _props = props,
      getUserConfirmation = _props.getUserConfirmation,
      _props$initialEntries = _props.initialEntries,
      initialEntries = _props$initialEntries === void 0 ? ['/'] : _props$initialEntries,
      _props$initialIndex = _props.initialIndex,
      initialIndex = _props$initialIndex === void 0 ? 0 : _props$initialIndex,
      _props$keyLength = _props.keyLength,
      keyLength = _props$keyLength === void 0 ? 6 : _props$keyLength;
  var transitionManager = createTransitionManager();

  function setState(nextState) {
    _extends(history, nextState);

    history.length = history.entries.length;
    transitionManager.notifyListeners(history.location, history.action);
  }

  function createKey() {
    return Math.random().toString(36).substr(2, keyLength);
  }

  var index = clamp(initialIndex, 0, initialEntries.length - 1);
  var entries = initialEntries.map(function (entry) {
    return typeof entry === 'string' ? createLocation(entry, undefined, createKey()) : createLocation(entry, undefined, entry.key || createKey());
  }); // Public interface

  var createHref = createPath;

  function push(path, state) {
    warning(!(typeof path === 'object' && path.state !== undefined && state !== undefined), 'You should avoid providing a 2nd state argument to push when the 1st ' + 'argument is a location-like object that already has state; it is ignored');
    var action = 'PUSH';
    var location = createLocation(path, state, createKey(), history.location);
    transitionManager.confirmTransitionTo(location, action, getUserConfirmation, function (ok) {
      if (!ok) return;
      var prevIndex = history.index;
      var nextIndex = prevIndex + 1;
      var nextEntries = history.entries.slice(0);

      if (nextEntries.length > nextIndex) {
        nextEntries.splice(nextIndex, nextEntries.length - nextIndex, location);
      } else {
        nextEntries.push(location);
      }

      setState({
        action: action,
        location: location,
        index: nextIndex,
        entries: nextEntries
      });
    });
  }

  function replace(path, state) {
    warning(!(typeof path === 'object' && path.state !== undefined && state !== undefined), 'You should avoid providing a 2nd state argument to replace when the 1st ' + 'argument is a location-like object that already has state; it is ignored');
    var action = 'REPLACE';
    var location = createLocation(path, state, createKey(), history.location);
    transitionManager.confirmTransitionTo(location, action, getUserConfirmation, function (ok) {
      if (!ok) return;
      history.entries[history.index] = location;
      setState({
        action: action,
        location: location
      });
    });
  }

  function go(n) {
    var nextIndex = clamp(history.index + n, 0, history.entries.length - 1);
    var action = 'POP';
    var location = history.entries[nextIndex];
    transitionManager.confirmTransitionTo(location, action, getUserConfirmation, function (ok) {
      if (ok) {
        setState({
          action: action,
          location: location,
          index: nextIndex
        });
      } else {
        // Mimic the behavior of DOM histories by
        // causing a render after a cancelled POP.
        setState();
      }
    });
  }

  function goBack() {
    go(-1);
  }

  function goForward() {
    go(1);
  }

  function canGo(n) {
    var nextIndex = history.index + n;
    return nextIndex >= 0 && nextIndex < history.entries.length;
  }

  function block(prompt) {
    if (prompt === void 0) {
      prompt = false;
    }

    return transitionManager.setPrompt(prompt);
  }

  function listen(listener) {
    return transitionManager.appendListener(listener);
  }

  var history = {
    length: entries.length,
    action: 'POP',
    location: entries[index],
    index: index,
    entries: entries,
    createHref: createHref,
    push: push,
    replace: replace,
    go: go,
    goBack: goBack,
    goForward: goForward,
    canGo: canGo,
    block: block,
    listen: listen
  };
  return history;
}

exports.createBrowserHistory = createBrowserHistory;
exports.createHashHistory = createHashHistory;
exports.createMemoryHistory = createMemoryHistory;
exports.createLocation = createLocation;
exports.locationsAreEqual = locationsAreEqual;
exports.parsePath = parsePath;
exports.createPath = createPath;