46 lines
1.5 KiB
JavaScript
46 lines
1.5 KiB
JavaScript
'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 aFunction = require('../internals/a-function');
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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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$({ target: 'AsyncIterator', proto: true, real: true }, {
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reduce: function reduce(reducer /* , initialValue */) {
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var iterator = anObject(this);
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var next = aFunction(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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aFunction(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(next.call(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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