@optimizely/nuclear-router/dist/utils.js

NuclearJS Router

"use strict";

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

/**
 * Variant of Promise.race(iterable)
 *
 * Given a list of Promises, return a Promise which resolves
 * with the index of the first Promise in the list which resolves
 * AND doesnt explicitly return false,
 * ensuring that all Promises before it have been settled.
 *
 * E.g.:
 *
 *   When the structure of promiseList is:
 *
 *   //   [<rejects in 1s>, <resolves in 1s>, <resolved>]
 *   // => Resolves with #2 after 1s
 *
 *   //   [<resolved>, <resolves in 1s>, <resolved>]
 *   // => Resolves with #1 immediately
 *
 *   //   [<rejects in 1s>, <rejected>, <resolved>]
 *   // => Resolves with #3 after 1s
 *
 *   //   [<rejected>, <resolves in 1s>, <resolved>]
 *   // => Resolves with #2 after 1s
 *
 *   //   [<resolves in 2s>, <resolves in 1s>, <resolved>]
 *   // => Resolves with #1 after 2s
 *
 * @param {Promise[]} promiseList
 * @returns {Promise}
 */
var PromiseOrderedFirst = exports.PromiseOrderedFirst = function PromiseOrderedFirst(promiseList) {
  return new Promise(function (resolve, reject) {
    var promiseToStateMap = [];
    var compute = function compute() {
      var _iteratorNormalCompletion = true;
      var _didIteratorError = false;
      var _iteratorError = undefined;

      try {
        for (var _iterator = promiseToStateMap[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
          var _step$value = _step.value,
              state = _step$value.state,
              res = _step$value.res,
              index = _step$value.index;

          if (state === "pending") {
            return;
          } else if (state === "resolved" && res !== false) {
            resolve({ res: res, index: index });
          }
        }
      } catch (err) {
        _didIteratorError = true;
        _iteratorError = err;
      } finally {
        try {
          if (!_iteratorNormalCompletion && _iterator.return) {
            _iterator.return();
          }
        } finally {
          if (_didIteratorError) {
            throw _iteratorError;
          }
        }
      }

      reject();
    };
    promiseList.forEach(function (promiseLike, index) {
      promiseToStateMap[index] = { state: "pending" };
      promiseLike.then(function (res) {
        promiseToStateMap[index] = { state: "resolved", res: res, index: index };
      }).catch(function (res) {
        promiseToStateMap[index] = { state: "rejected", res: res, index: index };
      }).then(compute, compute);
    });
    compute();
  });
};

exports.default = {
  PromiseOrderedFirst: PromiseOrderedFirst
};