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esnext.map.reduce.js
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esnext.map.reduce.js
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'use strict';
var $ = require('../internals/export');
var IS_PURE = require('../internals/is-pure');
var anObject = require('../internals/an-object');
var aFunction = require('../internals/a-function');
var getMapIterator = require('../internals/get-map-iterator');
var iterate = require('../internals/iterate');
// `Map.prototype.reduce` method
// https://github.com/tc39/proposal-collection-methods
$({ target: 'Map', proto: true, real: true, forced: IS_PURE }, {
reduce: function reduce(callbackfn /* , initialValue */) {
var map = anObject(this);
var iterator = getMapIterator(map);
var accumulator, step;
aFunction(callbackfn);
if (arguments.length > 1) accumulator = arguments[1];
else {
step = iterator.next();
if (step.done) throw TypeError('Reduce of empty map with no initial value');
accumulator = step.value[1];
}
iterate(iterator, function (key, value) {
accumulator = callbackfn(accumulator, value, key, map);
}, undefined, true, true);
return accumulator;
}
});