@uppy/utils/lib/emaFilter.test.js

Shared utility functions for Uppy Core and plugins maintained by the Uppy team.

import { describe, expect, it } from 'vitest';
import emaFilter from './emaFilter.js';
describe('emaFilter', () => {
    it('should calculate the exponential average', () => {
        expect(emaFilter(1, 0, 0, 1)).toBe(1);
        expect(emaFilter(1, 0, 2, 0)).toBe(0);
        expect(emaFilter(1, 0, 2, 2)).toBeCloseTo(0.5);
        expect(emaFilter(1, 0, 2, 4)).toBeCloseTo(0.75);
        expect(emaFilter(1, 0, 2, 6)).toBeCloseTo(0.875);
        expect(emaFilter(0, 1, 2, 2)).toBeCloseTo(0.5);
        expect(emaFilter(0, 1, 2, 4)).toBeCloseTo(0.25);
        expect(emaFilter(0, 1, 2, 6)).toBeCloseTo(0.125);
        expect(emaFilter(0.5, 1, 2, 4)).toBeCloseTo(0.625);
        expect(emaFilter(1, 0.5, 2, 4)).toBeCloseTo(0.875);
    });
    it('should behave like exponential moving average', () => {
        const firstValue = 1;
        const newValue = 10;
        const step = 0.618033989;
        const halfLife = 2;
        let lastFilteredValue = firstValue;
        for (let i = 0; i < 10; ++i) {
            lastFilteredValue = emaFilter(newValue, lastFilteredValue, halfLife, step);
            expect(lastFilteredValue).toBeCloseTo(emaFilter(newValue, firstValue, halfLife, step * (i + 1)));
        }
    });
});