locutus/esm/php/math/fmod.js

Locutus other languages' standard libraries to JavaScript for fun and educational purposes

export function fmod(x, y) {
    //      discuss at: https://locutus.io/php/fmod/
    // parity verified: PHP 8.3
    //     original by: Onno Marsman (https://twitter.com/onnomarsman)
    //        input by: Brett Zamir (https://brett-zamir.me)
    //     bugfixed by: Kevin van Zonneveld (https://kvz.io)
    //     bugfixed by: Irina (https://github.com/dekairi)
    //       example 1: fmod(5.7, 1.3)
    //       returns 1: 0.5
    //       example 2: fmod(10, 1)
    //       returns 2: 0
    let tmp;
    let tmp2;
    let p = 0;
    let pY = 0;
    let l = 0.0;
    let l2 = 0.0;
    const normalizedX = Number(x);
    const normalizedY = Number(y);
    tmp = normalizedX.toExponential().match(/^.\.?(.*)e(.+)$/);
    if (!tmp) {
        return NaN;
    }
    p = Number.parseInt(tmp[2] ?? '0', 10) - (tmp[1] ?? '').length;
    tmp = normalizedY.toExponential().match(/^.\.?(.*)e(.+)$/);
    if (!tmp) {
        return NaN;
    }
    pY = Number.parseInt(tmp[2] ?? '0', 10) - (tmp[1] ?? '').length;
    if (pY > p) {
        p = pY;
    }
    tmp2 = normalizedX % normalizedY;
    if (p < -100 || p > 20) {
        // toFixed will give an out of bound error so we fix it like this:
        l = Math.round(Math.log(tmp2) / Math.log(10));
        l2 = Math.pow(10, l);
        return Number((tmp2 / l2).toFixed(l - p)) * l2;
    }
    else {
        return parseFloat(tmp2.toFixed(Math.abs(p)));
    }
}