32 lines
1.1 KiB
JavaScript
32 lines
1.1 KiB
JavaScript
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import reduceBy from "./reduceBy.js";
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/**
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* Counts the elements of a list according to how many match each value of a
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* key generated by the supplied function. Returns an object mapping the keys
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* produced by `fn` to the number of occurrences in the list. Note that all
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* keys are coerced to strings because of how JavaScript objects work.
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*
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* Acts as a transducer if a transformer is given in list position.
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*
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* @func
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* @memberOf R
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* @since v0.1.0
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* @category Relation
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* @sig (a -> String) -> [a] -> {*}
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* @param {Function} fn The function used to map values to keys.
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* @param {Array} list The list to count elements from.
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* @return {Object} An object mapping keys to number of occurrences in the list.
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* @example
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*
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* const numbers = [1.0, 1.1, 1.2, 2.0, 3.0, 2.2];
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* R.countBy(Math.floor)(numbers); //=> {'1': 3, '2': 2, '3': 1}
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*
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* const letters = ['a', 'b', 'A', 'a', 'B', 'c'];
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* R.countBy(R.toLower)(letters); //=> {'a': 3, 'b': 2, 'c': 1}
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*/
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var countBy =
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/*#__PURE__*/
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reduceBy(function (acc, elem) {
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return acc + 1;
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}, 0);
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export default countBy;
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