Javascript color scale from 0% to 100%, rendering it from red to yellow to green to blue to magenta

color-scale.js

function colorScale(int) {
    let r, g, b = 0

    if (int >= 0 && int <= 20) {
      r = 255
      g = Math.round(12.75 * int)
      b = 0
    } else if (int > 20 && int <= 40) {
      r = Math.round(-12.75 * int + 510)
      g = 255
      b = 0
    } else if (int > 40 && int <= 60) {
      r = 0
      g = 255
      b = Math.round(12.75 * int) - 510
    } else if (int > 60 && int <= 80) {
      r = 0
      g = Math.round(-12.75 * int + 1020)
      b = 255
    } else {
      r = Math.round(12.75 * int - 1020)
      g = 0
      b = 255
    }

    const h = r * 0x10000 + g * 0x100 + b * 0x1
    return '#' + ('000000' + h.toString(16)).slice(-6)
}