| 'use strict'; |
| // https://github.com/tc39/proposal-iterator-helpers |
| var $ = require('../internals/export'); |
| var aFunction = require('../internals/a-function'); |
| var anObject = require('../internals/an-object'); |
| var getIteratorMethod = require('../internals/get-iterator-method'); |
| var createIteratorProxy = require('../internals/iterator-create-proxy'); |
| var callWithSafeIterationClosing = require('../internals/call-with-safe-iteration-closing'); |
| |
| var IteratorProxy = createIteratorProxy(function (arg) { |
| var iterator = this.iterator; |
| var result, mapped, iteratorMethod, innerIterator; |
| |
| while (true) { |
| if (innerIterator = this.innerIterator) { |
| result = anObject(this.innerNext.call(innerIterator)); |
| if (!result.done) return result.value; |
| this.innerIterator = this.innerNext = null; |
| } |
| |
| result = anObject(this.next.call(iterator, arg)); |
| |
| if (this.done = !!result.done) return; |
| |
| mapped = callWithSafeIterationClosing(iterator, this.mapper, result.value); |
| iteratorMethod = getIteratorMethod(mapped); |
| |
| if (iteratorMethod === undefined) { |
| throw TypeError('.flatMap callback should return an iterable object'); |
| } |
| |
| this.innerIterator = innerIterator = anObject(iteratorMethod.call(mapped)); |
| this.innerNext = aFunction(innerIterator.next); |
| } |
| }); |
| |
| $({ target: 'Iterator', proto: true, real: true }, { |
| flatMap: function flatMap(mapper) { |
| return new IteratorProxy({ |
| iterator: anObject(this), |
| mapper: aFunction(mapper), |
| innerIterator: null, |
| innerNext: null |
| }); |
| } |
| }); |