Darken a color in hex useful for dynamically creating a hover effect using only js. Ex: handleDarkenColor('#21FEEB') or handleDarkenColor('#ccc')

handleDarkenColor.js

function handleDarkenColor(hex) {
    let strHex = hex
    if(![4, 7].includes(hex.length)) return '#171773'
    else if(hex.length == 4) {
        let newHex = '#'
        hex.slice(1).split("").forEach((c) => {
            newHex += c + c
        })
        strHex = newHex
    }
    let rgb = [
        [1, 3],
        [3, 5],
        [5, 7]
    ]
    let int
    rgb = rgb.map(attr => {
        int = parseInt(strHex.slice(attr[0], attr[1]), 16)
        int = int - 50 >= 0 ? int - 50 : 0
        return int.toString(16).padStart(2, '0')
    })
    return `#${rgb.join('')}`
}