36 lines
1.6 KiB
JavaScript
36 lines
1.6 KiB
JavaScript
define(['./identity', './_cb', './find'], function (identity, _cb, find) {
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// The general algorithm behind `_.min` and `_.max`. `compare` should return
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// `true` if its first argument is more extreme than (i.e., should be preferred
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// over) its second argument, `false` otherwise. `iteratee` and `context`, like
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// in other collection functions, let you map the actual values in `collection`
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// to the values to `compare`. `decide` is an optional customization point
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// which is only present for historical reasons; please don't use it, as it will
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// likely be removed in the future.
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function extremum(collection, compare, iteratee, context, decide) {
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decide || (decide = identity);
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// `extremum` is essentially a combined map+reduce with **two** accumulators:
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// `result` and `iterResult`, respectively the unmapped and the mapped version
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// corresponding to the same element.
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var result, iterResult;
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iteratee = _cb(iteratee, context);
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var first = true;
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find(collection, function(value, key) {
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var iterValue = iteratee(value, key, collection);
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if (first || compare(iterValue, iterResult)) {
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result = value;
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iterResult = iterValue;
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first = false;
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}
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});
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// `extremum` normally returns an unmapped element from `collection`. However,
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// `_.min` and `_.max` forcibly return a number even if there is no element
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// that maps to a numeric value. Passing both accumulators through `decide`
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// before returning enables this behavior.
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return decide(result, iterResult);
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}
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return extremum;
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});
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