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48 lines
1.6 KiB
48 lines
1.6 KiB
'use strict'; |
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// https://github.com/tc39/proposal-iterator-helpers |
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var $ = require('../internals/export'); |
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var call = require('../internals/function-call'); |
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var aCallable = require('../internals/a-callable'); |
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var anObject = require('../internals/an-object'); |
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var getBuiltIn = require('../internals/get-built-in'); |
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var Promise = getBuiltIn('Promise'); |
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var $TypeError = TypeError; |
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$({ target: 'AsyncIterator', proto: true, real: true, forced: true }, { |
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reduce: function reduce(reducer /* , initialValue */) { |
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var iterator = anObject(this); |
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var next = aCallable(iterator.next); |
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var noInitial = arguments.length < 2; |
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var accumulator = noInitial ? undefined : arguments[1]; |
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aCallable(reducer); |
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return new Promise(function (resolve, reject) { |
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var loop = function () { |
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try { |
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Promise.resolve(anObject(call(next, iterator))).then(function (step) { |
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try { |
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if (anObject(step).done) { |
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noInitial ? reject($TypeError('Reduce of empty iterator with no initial value')) : resolve(accumulator); |
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} else { |
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var value = step.value; |
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if (noInitial) { |
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noInitial = false; |
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accumulator = value; |
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loop(); |
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} else { |
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Promise.resolve(reducer(accumulator, value)).then(function (result) { |
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accumulator = result; |
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loop(); |
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}, reject); |
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} |
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} |
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} catch (err) { reject(err); } |
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}, reject); |
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} catch (error) { reject(error); } |
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}; |
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loop(); |
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}); |
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} |
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});
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