41 lines
1.3 KiB
JavaScript
41 lines
1.3 KiB
JavaScript
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var aFunction = require('../internals/a-function');
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var toObject = require('../internals/to-object');
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var IndexedObject = require('../internals/indexed-object');
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var toLength = require('../internals/to-length');
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// `Array.prototype.{ reduce, reduceRight }` methods implementation
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var createMethod = function (IS_RIGHT) {
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return function (that, callbackfn, argumentsLength, memo) {
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aFunction(callbackfn);
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var O = toObject(that);
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var self = IndexedObject(O);
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var length = toLength(O.length);
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var index = IS_RIGHT ? length - 1 : 0;
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var i = IS_RIGHT ? -1 : 1;
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if (argumentsLength < 2) while (true) {
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if (index in self) {
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memo = self[index];
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index += i;
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break;
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}
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index += i;
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if (IS_RIGHT ? index < 0 : length <= index) {
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throw TypeError('Reduce of empty array with no initial value');
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}
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}
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for (;IS_RIGHT ? index >= 0 : length > index; index += i) if (index in self) {
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memo = callbackfn(memo, self[index], index, O);
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}
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return memo;
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};
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};
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module.exports = {
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// `Array.prototype.reduce` method
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// https://tc39.es/ecma262/#sec-array.prototype.reduce
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left: createMethod(false),
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// `Array.prototype.reduceRight` method
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// https://tc39.es/ecma262/#sec-array.prototype.reduceright
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right: createMethod(true)
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};
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