29 lines
1.0 KiB
JavaScript
29 lines
1.0 KiB
JavaScript
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import isArrayLike from './_isArrayLike.js';
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import keys from './keys.js';
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import optimizeCb from './_optimizeCb.js';
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// Internal helper to create a reducing function, iterating left or right.
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export default function createReduce(dir) {
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// Wrap code that reassigns argument variables in a separate function than
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// the one that accesses `arguments.length` to avoid a perf hit. (#1991)
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var reducer = function(obj, iteratee, memo, initial) {
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var _keys = !isArrayLike(obj) && keys(obj),
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length = (_keys || obj).length,
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index = dir > 0 ? 0 : length - 1;
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if (!initial) {
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memo = obj[_keys ? _keys[index] : index];
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index += dir;
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}
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for (; index >= 0 && index < length; index += dir) {
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var currentKey = _keys ? _keys[index] : index;
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memo = iteratee(memo, obj[currentKey], currentKey, obj);
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}
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return memo;
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};
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return function(obj, iteratee, memo, context) {
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var initial = arguments.length >= 3;
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return reducer(obj, optimizeCb(iteratee, context, 4), memo, initial);
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};
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}
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