23 lines
395 B
JavaScript
23 lines
395 B
JavaScript
/**
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* @param {Function} fn
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* @return {Array}
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*/
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Array.prototype.groupBy = function(fn) {
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let grouped = new Object();
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for (let x of this) {
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let key = fn(x);
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if (grouped[key] === undefined) {
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grouped[key] = new Array();
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}
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grouped[key].push(x);
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}
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return grouped;
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};
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/**
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* [1,2,3].groupBy(String) // {"1":[1],"2":[2],"3":[3]}
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*/
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