esnext.async-iterator.take.js 1.8 KB

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  1. 'use strict';
  2. var $ = require('../internals/export');
  3. var call = require('../internals/function-call');
  4. var anObject = require('../internals/an-object');
  5. var getIteratorDirect = require('../internals/get-iterator-direct');
  6. var getMethod = require('../internals/get-method');
  7. var notANaN = require('../internals/not-a-nan');
  8. var toPositiveInteger = require('../internals/to-positive-integer');
  9. var createAsyncIteratorProxy = require('../internals/async-iterator-create-proxy');
  10. var createIterResultObject = require('../internals/create-iter-result-object');
  11. var AsyncIteratorProxy = createAsyncIteratorProxy(function (Promise) {
  12. var state = this;
  13. var iterator = state.iterator;
  14. var returnMethod;
  15. if (!state.remaining--) {
  16. var resultDone = createIterResultObject(undefined, true);
  17. state.done = true;
  18. returnMethod = getMethod(iterator, 'return');
  19. if (returnMethod !== undefined) {
  20. return Promise.resolve(call(returnMethod, iterator)).then(function (result) {
  21. anObject(result);
  22. return resultDone;
  23. });
  24. }
  25. return resultDone;
  26. } return Promise.resolve(call(state.next, iterator)).then(function (step) {
  27. if (anObject(step).done) {
  28. state.done = true;
  29. return createIterResultObject(undefined, true);
  30. } return createIterResultObject(step.value, false);
  31. }).then(null, function (error) {
  32. state.done = true;
  33. throw error;
  34. });
  35. });
  36. // `AsyncIterator.prototype.take` method
  37. // https://github.com/tc39/proposal-async-iterator-helpers
  38. $({ target: 'AsyncIterator', proto: true, real: true, forced: true }, {
  39. take: function take(limit) {
  40. anObject(this);
  41. var remaining = toPositiveInteger(notANaN(+limit));
  42. return new AsyncIteratorProxy(getIteratorDirect(this), {
  43. remaining: remaining
  44. });
  45. }
  46. });