async异步 await等待

/**
 * Copyright (c) 2014-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

var regeneratorRuntime = (function (exports) {
   
  "use strict";

  var Op = Object.prototype;
  var hasOwn = Op.hasOwnProperty;
  var undefined; // More compressible than void 0.
  var $Symbol = typeof Symbol === "function" ? Symbol : {
   };
  var iteratorSymbol = $Symbol.iterator || "@@iterator";
  var asyncIteratorSymbol = $Symbol.asyncIterator || "@@asyncIterator";
  var toStringTagSymbol = $Symbol.toStringTag || "@@toStringTag";

  function wrap(innerFn, outerFn, self, tryLocsList) {
   
    // If outerFn provided and outerFn.prototype is a Generator, then outerFn.prototype instanceof Generator.
    var protoGenerator = outerFn && outerFn.prototype instanceof Generator ? outerFn : Generator;
    var generator = Object.create(protoGenerator.prototype);
    var context = new Context(tryLocsList || []);

    // The ._invoke method unifies the implementations of the .next,
    // .throw, and .return methods.
    generator._invoke = makeInvokeMethod(innerFn, self, context);

    return generator;
  }
  exports.wrap = wrap;

  // Try/catch helper to minimize deoptimizations. Returns a completion
  // record like context.tryEntries[i].completion. This interface could
  // have been (and was previously) designed to take a closure to be
  // invoked without arguments, but in all the cases we care about we
  // already have an existing method we want to call, so there's no need
  // to create a new function object. We can even get away with assuming
  // the method takes exactly one argument, since that happens to be true
  // in every case, so we don't have to touch the arguments object. The
  // only additional allocation required is the completion record, which
  // has a stable shape and so hopefully should be cheap to allocate.
  function tryCatch(fn, obj, arg) {
   
    try {
   
      return {
    type: "normal", arg: fn.call(obj, arg) };
    } catch (err) {
   
      return {
    type: "throw", arg: err };
    }
  }

  var GenStateSuspendedStart = "suspendedStart";
  var GenStateSuspendedYield = "suspendedYield";
  var GenStateExecuting = "executing";
  var GenStateCompleted = "completed";

  // Returning this object from the innerFn has the same effect as
  // breaking out of the dispatch switch statement.
  var ContinueSentinel = {
   };

  // Dummy constructor functions that we use as the .constructor and
  // .constructor.prototype properties for functions that return Generator
  // objects. For full spec compliance, you may wish to configure your
  // minifier not to mangle the names of these two functions.
  function Generator() {
   }
  function GeneratorFunction() {
   }
  function GeneratorFunctionPrototype() {
   }

  // This is a polyfill for %IteratorPrototype% for environments that
  // don't natively support it.
  var IteratorPrototype = {};
  IteratorPrototype[iteratorSymbol] = function () {
    return this;
  };

  var getProto = Object.getPrototypeOf;
  var NativeIteratorPrototype = getProto && getProto(getProto(values([])));
  if (NativeIteratorPrototype &&
      NativeIteratorPrototype !== Op &&
      hasOwn.call(NativeIteratorPrototype, iteratorSymbol)) {
    // This environment has a native %IteratorPrototype%; use it instead
    // of the polyfill.
    IteratorPrototype = NativeIteratorPrototype;
  }

  var Gp = GeneratorFunctionPrototype.prototype =
    Generator.prototype = Object.create(IteratorPrototype);
  GeneratorFunction.prototype = Gp.constructor = GeneratorFunctionPrototype;
  GeneratorFunctionPrototype.constructor = GeneratorFunction;
  GeneratorFunctionPrototype[toStringTagSymbol] =
    GeneratorFunction.displayName = "GeneratorFunction";

  // Helper for defining the .next, .throw, and .return methods of the
  // Iterator interface in terms of a single ._invoke method.
  function defineIteratorMethods(prototype) {
    ["next", "throw", "return"].forEach(function(method) {
      prototype[method] = function(arg) {
        return this._invoke(method, arg);
      };
    });
  }

  exports.isGeneratorFunction = function(genFun) {
    var ctor = typeof genFun === "function" && genFun.constructor;
    return ctor
      ? ctor === GeneratorFunction ||
        // For the native GeneratorFunction constructor, the best we can
        // do is to check its .name property.
        (ctor.displayName || ctor.name) === "GeneratorFunction"
      : false;
  };

  exports.mark = function(genFun) {
    if (Object.setPrototypeOf) {
      Object.setPrototypeOf(genFun, GeneratorFunctionPrototype);
    } else {
      genFun.__proto__ = GeneratorFunctionPrototype;
      if (!(toStringTagSymbol in genFun)) {
        genFun[toStringTagSymbol] = "GeneratorFunction";
      }
    }
    genFun.prototype = Object.create(Gp);
    return genFun;
  };

  // Within the body of any async function, `await x` is transformed to
  // `yield regeneratorRuntime.awrap(x)`, so that the runtime can test
  // `hasOwn.call(value, "__await")` to determine if the yielded value is
  // meant to be awaited.
  exports.awrap = function(arg) {
    return { __await: arg };
  };

  function AsyncIterator(generator) {
    function invoke(method, arg, resolve, reject) {
      var record = tryCatch(generator[method], generator, arg);
      if (record.type ===