approximate-aspect-ratio.js

/**
 * Usage:
 *
 * const ratio = approximateAspectRatio(855, 482, 20);
 * // "16:9"
 *
 * @param number width
 * @param number height
 * @param number maxRatio
 * @return string
 */
function approximateAspectRatio(width, height, maxRatio = 20) {
    const targetRatio = width / height;
    let closestRatio = '';
    let closestRatioDifference = Infinity;

    for (let i = 1; i <= maxRatio; i++) {
        const j = Math.round(i / targetRatio);
        const ratio = i / j;
        const difference = Math.abs(targetRatio - ratio);

        if (difference < closestRatioDifference) {
            closestRatioDifference = difference;
            closestRatio = `${i}:${j}`;
        }
    }

    return closestRatio;
}