@tidyjs/tidy/dist/es/distinct.js

Tidy up your data with JavaScript, inspired by dplyr and the tidyverse

import { singleOrArray } from './helpers/singleOrArray.js';

function distinct(keys) {
  const _distinct = (items) => {
    keys = singleOrArray(keys);
    if (!keys.length) {
      const set = new Set();
      for (const item of items) {
        set.add(item);
      }
      return Array.from(set);
    }
    const rootMap = new Map();
    const distinctItems = [];
    const lastKey = keys[keys.length - 1];
    for (const item of items) {
      let map = rootMap;
      let hasItem = false;
      for (const key of keys) {
        const mapItemKey = typeof key === "function" ? key(item) : item[key];
        if (key === lastKey) {
          hasItem = map.has(mapItemKey);
          if (!hasItem) {
            distinctItems.push(item);
            map.set(mapItemKey, true);
          }
          break;
        }
        if (!map.has(mapItemKey)) {
          map.set(mapItemKey, new Map());
        }
        map = map.get(mapItemKey);
      }
    }
    return distinctItems;
  };
  return _distinct;
}

export { distinct };
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