regeneratorRuntime 运行环境配置

注意710行与711行有做变更，代码来源于babel官网
https://babeljs.io/docs/en/learn
https://babeljs.io/repl

/**
 * 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 runtime = (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 === "throw") {
        reject(record.arg);
      } else {
        var result = record.arg;
        var value = result.value;
        if (value &&
            typeof value === "object" &&
            hasOwn.call(value, "__await")) {
          return Promise.resolve(value.__await).then(function(value) {
            invoke("next", value, resolve, reject);
          }, function(err) {
            invoke("throw", err, resolve, reject);
          });
        }
        return Promise.resolve(value).then(function(unwrapped) {
          // When a yielded Promise is resolved, its final value becomes
          // the .value of the Promise<{value,done}> result for the
          // current iteration.
          result.value = unwrapped;
          resolve(result);
        }, function(error) {
          // If a rejected Promise was yielded, throw the rejection back
          // into the async generator function so it can be handled there.
          return invoke("throw", error, resolve, reject);
        });
      }
    }
    var previousPromise;
    function enqueue(method, arg) {
      function callInvokeWithMethodAndArg() {
        return new Promise(function(resolve, reject) {
          invoke(method, arg, resolve, reject);
        });
      }
      return previousPromise =
        // If enqueue has been called before, then we want to wait until
        // all previous Promises have been resolved before calling invoke,
        // so that results are always delivered in the correct order. If
        // enqueue has not been called before, then it is important to
        // call invoke immediately, without waiting on a callback to fire,
        // so that the async generator function has the opportunity to do
        // any necessary setup in a predictable way. This predictability
        // is why the Promise constructor synchronously invokes its
        // executor callback, and why async functions synchronously
        // execute code before the first await. Since we implement simple
        // async functions in terms of async generators, it is especially
        // important to get this right, even though it requires care.
        previousPromise ? previousPromise.then(
          callInvokeWithMethodAndArg,
          // Avoid propagating failures to Promises returned by later
          // invocations of the iterator.
          callInvokeWithMethodAndArg
        ) : callInvokeWithMethodAndArg();
    }
    // Define the unified helper method that is used to implement .next,
    // .throw, and .return (see defineIteratorMethods).
    this._invoke = enqueue;
  }
  defineIteratorMethods(AsyncIterator.prototype);
  AsyncIterator.prototype[asyncIteratorSymbol] = function () {
    return this;
  };
  exports.AsyncIterator = AsyncIterator;
  // Note that simple async functions are implemented on top of
  // AsyncIterator objects; they just return a Promise for the value of
  // the final result produced by the iterator.
  exports.async = function(innerFn, outerFn, self, tryLocsList) {
    var iter = new AsyncIterator(
      wrap(innerFn, outerFn, self, tryLocsList)
    );
    return exports.isGeneratorFunction(outerFn)
      ? iter // If outerFn is a generator, return the full iterator.
      : iter.next().then(function(result) {
          return result.done ? result.value : iter.next();
        });
  };
  function makeInvokeMethod(innerFn, self, context) {
    var state = GenStateSuspendedStart;
    return function invoke(method, arg) {
      if (state === GenStateExecuting) {
        throw new Error("Generator is already running");
      }
      if (state === GenStateCompleted) {
        if (method === "throw") {
          throw arg;
        }
        // Be forgiving, per 25.3.3.3.3 of the spec:
        // https://people.mozilla.org/~jorendorff/es6-draft.html#sec-generatorresume
        return doneResult();
      }
      context.method = method;
      context.arg = arg;
      while (true) {
        var delegate = context.delegate;
        if (delegate) {
          var delegateResult = maybeInvokeDelegate(delegate, context);
          if (delegateResult) {
            if (delegateResult === ContinueSentinel) continue;
            return delegateResult;
          }
        }
        if (context.method === "next") {
          // Setting context._sent for legacy support of Babel's
          // function.sent implementation.
          context.sent = context._sent = context.arg;
        } else if (context.method === "throw") {
          if (state === GenStateSuspendedStart) {
            state = GenStateCompleted;
            throw context.arg;
          }
          context.dispatchException(context.arg);
        } else if (context.method === "return") {
          context.abrupt("return", context.arg);
        }
        state = GenStateExecuting;
        var record = tryCatch(innerFn, self, context);
        if (record.type === "normal") {
          // If an exception is thrown from innerFn, we leave state ===
          // GenStateExecuting and loop back for another invocation.
          state = context.done
            ? GenStateCompleted
            : GenStateSuspendedYield;
          if (record.arg === ContinueSentinel) {
            continue;
          }
          return {
            value: record.arg,
            done: context.done
          };
        } else if (record.type === "throw") {
          state = GenStateCompleted;
          // Dispatch the exception by looping back around to the
          // context.dispatchException(context.arg) call above.
          context.method = "throw";
          context.arg = record.arg;
        }
      }
    };
  }
  // Call delegate.iterator[context.method](context.arg) and handle the
  // result, either by returning a { value, done } result from the
  // delegate iterator, or by modifying context.method and context.arg,
  // setting context.delegate to null, and returning the ContinueSentinel.
  function maybeInvokeDelegate(delegate, context) {
    var method = delegate.iterator[context.method];
    if (method === undefined) {
      // A .throw or .return when the delegate iterator has no .throw
      // method always terminates the yield* loop.
      context.delegate = null;
      if (context.method === "throw") {
        // Note: ["return"] must be used for ES3 parsing compatibility.
        if (delegate.iterator["return"]) {
          // If the delegate iterator has a return method, give it a
          // chance to clean up.
          context.method = "return";
          context.arg = undefined;
          maybeInvokeDelegate(delegate, context);
          if (context.method === "throw") {
            // If maybeInvokeDelegate(context) changed context.method from
            // "return" to "throw", let that override the TypeError below.
            return ContinueSentinel;
          }
        }
        context.method = "throw";
        context.arg = new TypeError(
          "The iterator does not provide a 'throw' method");
      }
      return ContinueSentinel;
    }
    var record = tryCatch(method, delegate.iterator, context.arg);
    if (record.type === "throw") {
      context.method = "throw";
      context.arg = record.arg;
      context.delegate = null;
      return ContinueSentinel;
    }
    var info = record.arg;
    if (! info) {
      context.method = "throw";
      context.arg = new TypeError("iterator result is not an object");
      context.delegate = null;
      return ContinueSentinel;
    }
    if (info.done) {
      // Assign the result of the finished delegate to the temporary
      // variable specified by delegate.resultName (see delegateYield).
      context[delegate.resultName] = info.value;
      // Resume execution at the desired location (see delegateYield).
      context.next = delegate.nextLoc;
      // If context.method was "throw" but the delegate handled the
      // exception, let the outer generator proceed normally. If
      // context.method was "next", forget context.arg since it has been
      // "consumed" by the delegate iterator. If context.method was
      // "return", allow the original .return call to continue in the
      // outer generator.
      if (context.method !== "return") {
        context.method = "next";
        context.arg = undefined;
      }
    } else {
      // Re-yield the result returned by the delegate method.
      return info;
    }
    // The delegate iterator is finished, so forget it and continue with
    // the outer generator.
    context.delegate = null;
    return ContinueSentinel;
  }
  // Define Generator.prototype.{next,throw,return} in terms of the
  // unified ._invoke helper method.
  defineIteratorMethods(Gp);
  Gp[toStringTagSymbol] = "Generator";
  // A Generator should always return itself as the iterator object when the
  // @@iterator function is called on it. Some browsers' implementations of the
  // iterator prototype chain incorrectly implement this, causing the Generator
  // object to not be returned from this call. This ensures that doesn't happen.
  // See https://github.com/facebook/regenerator/issues/274 for more details.
  Gp[iteratorSymbol] = function() {
    return this;
  };
  Gp.toString = function() {
    return "[object Generator]";
  };
  function pushTryEntry(locs) {
    var entry = { tryLoc: locs[0] };
    if (1 in locs) {
      entry.catchLoc = locs[1];
    }
    if (2 in locs) {
      entry.finallyLoc = locs[2];
      entry.afterLoc = locs[3];
    }
    this.tryEntries.push(entry);
  }
  function resetTryEntry(entry) {
    var record = entry.completion || {};
    record.type = "normal";
    delete record.arg;
    entry.completion = record;
  }
  function Context(tryLocsList) {
    // The root entry object (effectively a try statement without a catch
    // or a finally block) gives us a place to store values thrown from
    // locations where there is no enclosing try statement.
    this.tryEntries = [{ tryLoc: "root" }];
    tryLocsList.forEach(pushTryEntry, this);
    this.reset(true);
  }
  exports.keys = function(object) {
    var keys = [];
    for (var key in object) {
      keys.push(key);
    }
    keys.reverse();
    // Rather than returning an object with a next method, we keep
    // things simple and return the next function itself.
    return function next() {
      while (keys.length) {
        var key = keys.pop();
        if (key in object) {
          next.value = key;
          next.done = false;
          return next;
        }
      }
      // To avoid creating an additional object, we just hang the .value
      // and .done properties off the next function object itself. This
      // also ensures that the minifier will not anonymize the function.
      next.done = true;
      return next;
    };
  };
  function values(iterable) {
    if (iterable) {
      var iteratorMethod = iterable[iteratorSymbol];
      if (iteratorMethod) {
        return iteratorMethod.call(iterable);
      }
      if (typeof iterable.next === "function") {
        return iterable;
      }
      if (!isNaN(iterable.length)) {
        var i = -1, next = function next() {
          while (++i < iterable.length) {
            if (hasOwn.call(iterable, i)) {
              next.value = iterable[i];
              next.done = false;
              return next;
            }
          }
          next.value = undefined;
          next.done = true;
          return next;
        };
        return next.next = next;
      }
    }
    // Return an iterator with no values.
    return { next: doneResult };
  }
  exports.values = values;
  function doneResult() {
    return { value: undefined, done: true };
  }
  Context.prototype = {
    constructor: Context,
    reset: function(skipTempReset) {
      this.prev = 0;
      this.next = 0;
      // Resetting context._sent for legacy support of Babel's
      // function.sent implementation.
      this.sent = this._sent = undefined;
      this.done = false;
      this.delegate = null;
      this.method = "next";
      this.arg = undefined;
      this.tryEntries.forEach(resetTryEntry);
      if (!skipTempReset) {
        for (var name in this) {
          // Not sure about the optimal order of these conditions:
          if (name.charAt(0) === "t" &&
              hasOwn.call(this, name) &&
              !isNaN(+name.slice(1))) {
            this[name] = undefined;
          }
        }
      }
    },
    stop: function() {
      this.done = true;
      var rootEntry = this.tryEntries[0];
      var rootRecord = rootEntry.completion;
      if (rootRecord.type === "throw") {
        throw rootRecord.arg;
      }
      return this.rval;
    },
    dispatchException: function(exception) {
      if (this.done) {
        throw exception;
      }
      var context = this;
      function handle(loc, caught) {
        record.type = "throw";
        record.arg = exception;
        context.next = loc;
        if (caught) {
          // If the dispatched exception was caught by a catch block,
          // then let that catch block handle the exception normally.
          context.method = "next";
          context.arg = undefined;
        }
        return !! caught;
      }
      for (var i = this.tryEntries.length - 1; i >= 0; --i) {
        var entry = this.tryEntries[i];
        var record = entry.completion;
        if (entry.tryLoc === "root") {
          // Exception thrown outside of any try block that could handle
          // it, so set the completion value of the entire function to
          // throw the exception.
          return handle("end");
        }
        if (entry.tryLoc <= this.prev) {
          var hasCatch = hasOwn.call(entry, "catchLoc");
          var hasFinally = hasOwn.call(entry, "finallyLoc");
          if (hasCatch && hasFinally) {
            if (this.prev < entry.catchLoc) {
              return handle(entry.catchLoc, true);
            } else if (this.prev < entry.finallyLoc) {
              return handle(entry.finallyLoc);
            }
          } else if (hasCatch) {
            if (this.prev < entry.catchLoc) {
              return handle(entry.catchLoc, true);
            }
          } else if (hasFinally) {
            if (this.prev < entry.finallyLoc) {
              return handle(entry.finallyLoc);
            }
          } else {
            throw new Error("try statement without catch or finally");
          }
        }
      }
    },
    abrupt: function(type, arg) {
      for (var i = this.tryEntries.length - 1; i >= 0; --i) {
        var entry = this.tryEntries[i];
        if (entry.tryLoc <= this.prev &&
            hasOwn.call(entry, "finallyLoc") &&
            this.prev < entry.finallyLoc) {
          var finallyEntry = entry;
          break;
        }
      }
      if (finallyEntry &&
          (type === "break" ||
           type === "continue") &&
          finallyEntry.tryLoc <= arg &&
          arg <= finallyEntry.finallyLoc) {
        // Ignore the finally entry if control is not jumping to a
        // location outside the try/catch block.
        finallyEntry = null;
      }
      var record = finallyEntry ? finallyEntry.completion : {};
      record.type = type;
      record.arg = arg;
      if (finallyEntry) {
        this.method = "next";
        this.next = finallyEntry.finallyLoc;
        return ContinueSentinel;
      }
      return this.complete(record);
    },
    complete: function(record, afterLoc) {
      if (record.type === "throw") {
        throw record.arg;
      }
      if (record.type === "break" ||
          record.type === "continue") {
        this.next = record.arg;
      } else if (record.type === "return") {
        this.rval = this.arg = record.arg;
        this.method = "return";
        this.next = "end";
      } else if (record.type === "normal" && afterLoc) {
        this.next = afterLoc;
      }
      return ContinueSentinel;
    },
    finish: function(finallyLoc) {
      for (var i = this.tryEntries.length - 1; i >= 0; --i) {
        var entry = this.tryEntries[i];
        if (entry.finallyLoc === finallyLoc) {
          this.complete(entry.completion, entry.afterLoc);
          resetTryEntry(entry);
          return ContinueSentinel;
        }
      }
    },
    "catch": function(tryLoc) {
      for (var i = this.tryEntries.length - 1; i >= 0; --i) {
        var entry = this.tryEntries[i];
        if (entry.tryLoc === tryLoc) {
          var record = entry.completion;
          if (record.type === "throw") {
            var thrown = record.arg;
            resetTryEntry(entry);
          }
          return thrown;
        }
      }
      // The context.catch method must only be called with a location
      // argument that corresponds to a known catch block.
      throw new Error("illegal catch attempt");
    },
    delegateYield: function(iterable, resultName, nextLoc) {
      this.delegate = {
        iterator: values(iterable),
        resultName: resultName,
        nextLoc: nextLoc
      };
      if (this.method === "next") {
        // Deliberately forget the last sent value so that we don't
        // accidentally pass it on to the delegate.
        this.arg = undefined;
      }
      return ContinueSentinel;
    }
  };
  // Regardless of whether this script is executing as a CommonJS module
  // or not, return the runtime object so that we can declare the variable
  // regeneratorRuntime in the outer scope, which allows this module to be
  // injected easily by `bin/regenerator --include-runtime script.js`.
  return exports;
}(
  // If this script is executing as a CommonJS module, use module.exports
  // as the regeneratorRuntime namespace. Otherwise create a new empty
  // object. Either way, the resulting object will be used to initialize
  // the regeneratorRuntime variable at the top of this file.
   /* true ? module.exports : undefined */
   { exports: {} }
));
try {
  regeneratorRuntime = runtime;
} catch (accidentalStrictMode) {
  // This module should not be running in strict mode, so the above
  // assignment should always work unless something is misconfigured. Just
  // in case runtime.js accidentally runs in strict mode, we can escape
  // strict mode using a global Function call. This could conceivably fail
  // if a Content Security Policy forbids using Function, but in that case
  // the proper solution is to fix the accidental strict mode problem. If
  // you've misconfigured your bundler to force strict mode and applied a
  // CSP to forbid Function, and you're not willing to fix either of those
  // problems, please detail your unique predicament in a GitHub issue.
  Function("r", "regeneratorRuntime = r")(runtime);
}

bable编译前的代码

function * demo (){
  console.log('1')
  var a = yield new Promise(function(resolve, reject){
    console.log('2');
    setTimeout(()=>{
        console.log('3');
        resolve(1);
    }, 3000);
  });
  console.log('4');
  var b = yield Promise.resolve(a + 1);
  console.log('5');
  var c = yield Promise.resolve(b + 1);
  return c;
}
function co(generator) {
  var gen = generator();
  function nextFunc(arg) {
  console.log('arg', arg);
    var next = gen.next(arg);
    if (!next.done) {
      next.value.then(function(data){
        console.log('data',data);
        nextFunc(data);
      });
    } else if (next.value) {
      console.log('return',next.value)
        return next.value;
    }
  }
  nextFunc();
}
co(demo);
arg undefined
VM672:2 1
VM672:4 2
undefined
VM672:6 3
VM672:23 data 1
VM672:19 arg 1
VM672:10 4
VM672:23 data 2
VM672:19 arg 2
VM672:12 5
VM672:23 data 3
VM672:19 arg 3
VM672:27 return 3

babel编译后的代码

"use strict";
var _marked =
/*#__PURE__*/
regeneratorRuntime.mark(demo);
function demo() {
  var a, b, c;
  return regeneratorRuntime.wrap(function demo$(_context) {
    while (1) {
      switch (_context.prev = _context.next) {
        case 0:
          _context.next = 2;
          return Promise.resolve(1);
        case 2:
          a = _context.sent;
          _context.next = 5;
          return Promise.resolve(a + 1);
        case 5:
          b = _context.sent;
          _context.next = 8;
          return Promise.resolve(b + 1);
        case 8:
          c = _context.sent;
          return _context.abrupt("return", c);
        case 10:
        case "end":
          return _context.stop();
      }
    }
  }, _marked);
}
function co(generator) {
  var gen = generator();
  function nextFunc(arg) {
    console.log('arg', arg);
    var next = gen.next(arg);
    if (!next.done) {
      next.value.then(function (data) {
        console.log('data', data);
        nextFunc(data);
      });
    } else if (next.value) {
      console.log('return', next.value);
      return next.value;
    }
  }
  nextFunc();
}
co(demo);

学习过的后的理解

1.创建3个构造函数，Generator，GeneratorFunction，GeneratorFunctionPrototype
2.首先将数组的Symbol.iterator的拿出来给上面的三个构造函数使用
3.var _marked = regeneratorRuntime.mark(demo); 方法将next与throw，return方法添加到demo里面，是demo的类型变成Generator类型
4.co是一个函数执行器，当完成第一个操作的时候，执行next方法执行第二个方法
5.demo是一个函数分配器，指定下一步执行什么处理

var regeneratorRuntime = (function (exports) {
  "use strict";
  function Generator() { };
  function GeneratorFunctionPrototype() { };
  function GeneratorFunction() { };
  var Op = Object.prototype;
  var $Symbol = typeof Symbol === 'function' ? Symbol : {};
  var iteratorSymbol = $Symbol.iterator || "@@iterator";
  var toStringTagSymbol = $Symbol.toStringTag || "@@toStringTag";
  var hasOwn = Object.hasOwnProperty;
  var getProto = Object.getPrototypeOf;
  ;;;;;;
  var IteratorPrototype = {};
  IteratorPrototype[iteratorSymbol] = function () {
    return this;
  }
  function values(iterable) {
    if (iterable) {
      var iteratorMethod = iterable[iteratorSymbol];
      if (iteratorMethod) {
        return iteratorMethod.call(iterable);
      }
    }
  }
  var NativeIteratorPrototype = getProto && getProto(getProto(values([])));
  if (NativeIteratorPrototype && NativeIteratorPrototype !== Op &&
    hasOwn.call(NativeIteratorPrototype, iteratorSymbol)) {
    ;;;;;
    // 将数组的 Array Iterator 给了 IteratorPrototype
    IteratorPrototype = NativeIteratorPrototype;
  }
  var Gp = GeneratorFunctionPrototype.prototype =
    Generator.prototype = Object.create(IteratorPrototype);
  GeneratorFunction.prototype = Gp.constructor = GeneratorFunctionPrototype;
  GeneratorFunctionPrototype.constructor = GeneratorFunction;
  GeneratorFunctionPrototype[toStringTagSymbol] =
    GeneratorFunction.displayName = "GeneratorFunction";
  defineIteratorMethods(Gp);
  Gp[toStringTagSymbol] = "Generator";
  Gp[iteratorSymbol] = function () {
    return this;
  };
  Gp.toString = function () {
    return "[object Generator]";
  };
  function defineIteratorMethods(prototype) {
    ['next', 'throw', 'return'].forEach(function (method) {
      ;;;;;
      prototype[method] = function (arg) {
        ;;;;;
        return this._invoke(method, arg);
      }
    });
  }
  exports.mark = function (genFun) {
    Object.setPrototypeOf(genFun, Generator);
    genFun.prototype = Object.create(Gp);
    return genFun;
  }
  exports.wrap = function (innerFn, outerFn) {
    // innerFn, outerFn
    var protoGenerator = outerFn && outerFn.prototype instanceof Generator ? outerFn : Generator;
    var generator = Object.create(protoGenerator.prototype);
    var context = new Context([]);
    generator._invoke = makeInvokeMethod(innerFn, self, context);
    return generator;
  }
  function tryCatch(fn, obj, arg) { // 公共的try catch
    ;;;;;;
    try {
      // arg 返回函数执行结果
      return { type: 'normal', arg: fn.call(obj, arg) };
    } catch (err) {
      return { type: 'throw', arg: err };
    }
  }
  function Context(arg) {
    this.arg = undefined;
    this.delegate = null;
    this.done = false;
    this.method = "next";
    this.next = 0;
    this.prev = 0;
    this.sent = undefined
    this.tryEntries = [];
    this._sent = undefined
  }
  // 一些状态值
  var GenStateSuspendedStart = "suspendedStart";
  var GenStateSuspendedYield = "suspendedYield";
  var GenStateExecuting = "executing";
  var GenStateCompleted = "completed";
  var ContinueSentinel = {};
  function makeInvokeMethod(innerFn, self, context) {
    var state = GenStateSuspendedStart;
    ;;;;;;
    return function invoke(method, arg) {
      ;;;;;;
      if (state === GenStateExecuting) {
        throw new Error("Generator is already running");
      }
      if (state === GenStateCompleted) {
        if (method === "throw") {
          throw arg;
        }
        return doneResult();
      }
      context.method = method;
      context.arg = arg;
      while (true) {
        state = GenStateExecuting;
        if (context.method === 'next') {
          context.sent = context._sent = context.arg;
        } else if (context.method === 'throw') {
          if (state === GenStateSuspendedStart) {
            state = GenStateCompleted;
            throw context.arg;
          }
          return {
            done: true,
            value: arg
          }
        } else if (context.method === 'return') {
          state = GenStateCompleted;
          return {
            done: true,
            value: arg
          }
        }
        var record = tryCatch(innerFn, self, context);
        state = GenStateExecuting;
        if (record.type === 'normal') {
          state = context.done
            ? GenStateCompleted
            : GenStateSuspendedYield;
          if (record.arg === ContinueSentinel) {
            continue;
          }
          return {
            value: record.arg,
            done: context.done
          }
        } else if (record.type === "throw") {
          state = GenStateCompleted;
          context.method = "throw";
          context.arg = record.arg;
        }
      }
    }
  }
  return exports;
})({ exports: {} });
var _marked =
  /*#__PURE__*/
  regeneratorRuntime.mark(demo);
function demo() {
  var a, b, c;
  return regeneratorRuntime.wrap(function demo$(_context) {
    while (1) {
      switch (_context.prev = _context.next) {
        case 0:
          _context.next = 2;
          return Promise.resolve(1);
        case 2:
          a = _context.sent;
          _context.next = 5;
          return Promise.resolve(a + 1);
        case 5:
          b = _context.sent;
          _context.next = 8;
          return Promise.resolve(b + 1);
        case 8:
          c = _context.sent;
          return _context.abrupt("return", c);
        case 10:
        case "end":
          return _context.stop();
      }
    }
  }, _marked);
}
function co(generator) {
  var gen = generator();
  function nextFunc(arg) {
    var next = gen.next(arg);
    console.log('next', next);
    if (!next.done) {
      next.value.then(function (data) {
        nextFunc(data);
      });
    } else if (next.value) {
      console.log('return', next.value);
      return next.value;
    }
  }
  nextFunc();
}
co(demo);