微信小程序中使用 async 和 await

在⼩程序的开发⼯具中，勾选 es6转es5语法
下载 facebook的regenerator库中的 regenerator/packages/regenerator-runtime/runtime.js
在⼩程序⽬录下新建⽂件夹 lib/runtime/runtime.js ，将代码拷⻉进去
在每⼀个需要使⽤async语法的⻚⾯js⽂件中，都引⼊（不能全局引⼊）

引入方式：

import regeneratorRuntime from '…/…/lib/runtime/runtime’

runtime.js 文件中需要拷贝的代码如下：(或者自己到github上去拷贝也可以，github连接地址在第二步上已给出)

/**

Copyright © 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 };
};

    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.iteratorcontext.method 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") {
    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.
typeof module === “object” ? module.exports : {}
));

到此就结束了，有啥不明白的或者说我有啥写错误的地方，欢迎各位前辈随时滴滴我 !!!

来源：CSDN

作者：一个技术小青年

链接：https://blog.csdn.net/qq_43353619/article/details/104069586

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