toAsync.js 1.6 KB

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  1. var toArr = require('./toArr');
  2. var isGeneratorFn = require('./isGeneratorFn');
  3. var isPromise = require('./isPromise');
  4. var toStr = require('./toStr');
  5. exports = function(fn) {
  6. if (!isGeneratorFn(fn)) {
  7. throw new TypeError('Expected a generator function');
  8. }
  9. return function() {
  10. var _this = this;
  11. var args = toArr(arguments);
  12. return new Promise(function(resolve, reject) {
  13. var generator = fn.apply(_this, args);
  14. function onFulfilled(res) {
  15. var ret;
  16. try {
  17. ret = generator.next(res);
  18. } catch (e) {
  19. return reject(e);
  20. }
  21. next(ret);
  22. }
  23. function onRejected(err) {
  24. var ret;
  25. try {
  26. ret = generator.throw(err);
  27. } catch (e) {
  28. return reject(e);
  29. }
  30. next(ret);
  31. }
  32. function next(ret) {
  33. if (ret.done) return resolve(ret.value);
  34. if (isPromise(ret.value)) {
  35. return ret.value.then(onFulfilled, onRejected);
  36. }
  37. return onRejected(
  38. new TypeError(
  39. 'You may only yield a promise, '.concat(
  40. toStr(ret.value),
  41. ' is passed'
  42. )
  43. )
  44. );
  45. }
  46. onFulfilled();
  47. });
  48. };
  49. };
  50. module.exports = exports;