react-router/es/computeChangedRoutes.js

A complete routing library for React

import { getParamNames } from './PatternUtils';

function routeParamsChanged(route, prevState, nextState) {
  if (!route.path) return false;

  var paramNames = getParamNames(route.path);

  return paramNames.some(function (paramName) {
    return prevState.params[paramName] !== nextState.params[paramName];
  });
}

/**
 * Returns an object of { leaveRoutes, changeRoutes, enterRoutes } determined by
 * the change from prevState to nextState. We leave routes if either
 * 1) they are not in the next state or 2) they are in the next state
 * but their params have changed (i.e. /users/123 => /users/456).
 *
 * leaveRoutes are ordered starting at the leaf route of the tree
 * we're leaving up to the common parent route. enterRoutes are ordered
 * from the top of the tree we're entering down to the leaf route.
 *
 * changeRoutes are any routes that didn't leave or enter during
 * the transition.
 */
function computeChangedRoutes(prevState, nextState) {
  var prevRoutes = prevState && prevState.routes;
  var nextRoutes = nextState.routes;

  var leaveRoutes = void 0,
      changeRoutes = void 0,
      enterRoutes = void 0;
  if (prevRoutes) {
    (function () {
      var parentIsLeaving = false;
      leaveRoutes = prevRoutes.filter(function (route) {
        if (parentIsLeaving) {
          return true;
        } else {
          var isLeaving = nextRoutes.indexOf(route) === -1 || routeParamsChanged(route, prevState, nextState);
          if (isLeaving) parentIsLeaving = true;
          return isLeaving;
        }
      });

      // onLeave hooks start at the leaf route.
      leaveRoutes.reverse();

      enterRoutes = [];
      changeRoutes = [];

      nextRoutes.forEach(function (route) {
        var isNew = prevRoutes.indexOf(route) === -1;
        var paramsChanged = leaveRoutes.indexOf(route) !== -1;

        if (isNew || paramsChanged) enterRoutes.push(route);else changeRoutes.push(route);
      });
    })();
  } else {
    leaveRoutes = [];
    changeRoutes = [];
    enterRoutes = nextRoutes;
  }

  return {
    leaveRoutes: leaveRoutes,
    changeRoutes: changeRoutes,
    enterRoutes: enterRoutes
  };
}

export default computeChangedRoutes;