7 lines
198 B
JavaScript
7 lines
198 B
JavaScript
const countBy = (arr, fn) =>
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arr.map(typeof fn === 'function' ? fn : val => val[fn]).reduce((acc, val) => {
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acc[val] = (acc[val] || 0) + 1;
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return acc;
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}, {});
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module.exports = countBy;
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