esnext.async-iterator.take.js 1.7 KB

1234567891011121314151617181920212223242526272829303132333435363738394041424344454647
  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 notANaN = require('../internals/not-a-nan');
  7. var toPositiveInteger = require('../internals/to-positive-integer');
  8. var createAsyncIteratorProxy = require('../internals/async-iterator-create-proxy');
  9. var createIterResultObject = require('../internals/create-iter-result-object');
  10. var AsyncIteratorProxy = createAsyncIteratorProxy(function (Promise) {
  11. var state = this;
  12. var iterator = state.iterator;
  13. var returnMethod;
  14. if (!state.remaining--) {
  15. var resultDone = createIterResultObject(undefined, true);
  16. state.done = true;
  17. returnMethod = iterator['return'];
  18. if (returnMethod !== undefined) {
  19. return Promise.resolve(call(returnMethod, iterator, undefined)).then(function () {
  20. return resultDone;
  21. });
  22. }
  23. return resultDone;
  24. } return Promise.resolve(call(state.next, iterator)).then(function (step) {
  25. if (anObject(step).done) {
  26. state.done = true;
  27. return createIterResultObject(undefined, true);
  28. } return createIterResultObject(step.value, false);
  29. }).then(null, function (error) {
  30. state.done = true;
  31. throw error;
  32. });
  33. });
  34. // `AsyncIterator.prototype.take` method
  35. // https://github.com/tc39/proposal-async-iterator-helpers
  36. $({ target: 'AsyncIterator', proto: true, real: true, forced: true }, {
  37. take: function take(limit) {
  38. anObject(this);
  39. var remaining = toPositiveInteger(notANaN(+limit));
  40. return new AsyncIteratorProxy(getIteratorDirect(this), {
  41. remaining: remaining
  42. });
  43. }
  44. });