74 lines
2.6 KiB
JavaScript
74 lines
2.6 KiB
JavaScript
import _clone from "./internal/_clone.js";
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import _curryN from "./internal/_curryN.js";
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import _dispatchable from "./internal/_dispatchable.js";
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import _has from "./internal/_has.js";
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import _reduced from "./internal/_reduced.js";
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import _xReduce from "./internal/_xReduce.js";
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import _xreduceBy from "./internal/_xreduceBy.js";
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import _xwrap from "./internal/_xwrap.js";
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/**
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* Groups the elements of the list according to the result of calling
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* the String-returning function `keyFn` on each element and reduces the elements
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* of each group to a single value via the reducer function `valueFn`.
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*
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* The value function receives two values: *(acc, value)*. It may use
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* [`R.reduced`](#reduced) to short circuit the iteration.
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*
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* This function is basically a more general [`groupBy`](#groupBy) function.
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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 v0.20.0
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* @category List
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* @sig ((a, b) -> a) -> a -> (b -> String) -> [b] -> {String: a}
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* @param {Function} valueFn The function that reduces the elements of each group to a single
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* value. Receives two values, accumulator for a particular group and the current element.
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* @param {*} acc The (initial) accumulator value for each group.
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* @param {Function} keyFn The function that maps the list's element into a key.
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* @param {Array} list The array to group.
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* @return {Object} An object with the output of `keyFn` for keys, mapped to the output of
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* `valueFn` for elements which produced that key when passed to `keyFn`.
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* @see R.groupBy, R.reduce, R.reduced
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* @example
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*
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* const groupNames = (acc, {name}) => acc.concat(name)
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* const toGrade = ({score}) =>
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* score < 65 ? 'F' :
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* score < 70 ? 'D' :
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* score < 80 ? 'C' :
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* score < 90 ? 'B' : 'A'
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*
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* var students = [
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* {name: 'Abby', score: 83},
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* {name: 'Bart', score: 62},
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* {name: 'Curt', score: 88},
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* {name: 'Dora', score: 92},
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* ]
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*
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* reduceBy(groupNames, [], toGrade, students)
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* //=> {"A": ["Dora"], "B": ["Abby", "Curt"], "F": ["Bart"]}
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*/
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var reduceBy =
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/*#__PURE__*/
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_curryN(4, [],
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/*#__PURE__*/
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_dispatchable([], _xreduceBy, function reduceBy(valueFn, valueAcc, keyFn, list) {
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var xf = _xwrap(function (acc, elt) {
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var key = keyFn(elt);
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var value = valueFn(_has(key, acc) ? acc[key] : _clone(valueAcc, false), elt);
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if (value && value['@@transducer/reduced']) {
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return _reduced(acc);
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}
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acc[key] = value;
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return acc;
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});
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return _xReduce(xf, {}, list);
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}));
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export default reduceBy; |