everyutil/array/findAnomalies.js

A comprehensive library of lightweight, reusable utility functions for JavaScript and TypeScript, designed to streamline common programming tasks such as string manipulation, array processing, date handling, and more.

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.findAnomalies = void 0;
/**
 * Finds values that differ statistically or structurally.
 * @author @dailker
 * @param {any[]} array
 * @param {object} [options]
 * @returns {any[]}
 */
function findAnomalies(array, options) {
    if (options?.zScore && array.every(x => typeof x === 'number')) {
        const mean = array.reduce((a, b) => a + b, 0) / array.length;
        const std = Math.sqrt(array.reduce((a, b) => a + Math.pow(b - mean, 2), 0) / array.length);
        return array.filter(x => Math.abs((x - mean) / (std || 1)) > 2);
    }
    // Type anomaly: lone type
    const typeGroups = array.reduce((acc, v) => {
        const t = typeof v;
        acc[t] = (acc[t] || 0) + 1;
        return acc;
    }, {});
    const rareTypes = Object.entries(typeGroups).filter(([_, c]) => c === 1).map(([t]) => t);
    return array.filter(x => rareTypes.includes(typeof x));
}
exports.findAnomalies = findAnomalies;