Check if color is lighter or darker. Remove the comments and you can use the power of types (optional)

is-light.js

// This file is Typescript friendly
// Which means you can replace the function signatures and get 
// the power of types in your WebApp 🔋

// const hexToRgb = (colorinHex: string): [number, number, number] | [] => {
const hexToRgb = (colorinHex) => {
  // Expand shorthand form (e.g. "03F") to full form (e.g. "0033FF")
  const expandShorthandHexToFullForm = /^#?([a-f\d])([a-f\d])([a-f\d])$/i;
  const hex = colorinHex.replace(expandShorthandHexToFullForm, (m, r, g, b) => r + r + g + g + b + b);

  const result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);

  return result ? [parseInt(result[1], 16), parseInt(result[2], 16), parseInt(result[3], 16)] : [];
};

// export const isLight(colorinHex: string): boolean {
export const isLight(colorinHex) {
  const [red, green, blue] = hexToRgb(colorinHex);
  // Displaying an error in case something goes wrong during tranformation  
  if (!red || !green || !blue) {
    throw new Error(`Unable to transform ${colorinHex} to hex.`);
  }

  const brightness = (red * 299 + green * 587 + blue * 114) / 1000;
  // If it's not light, that means it's dark
  return brightness > 128;
};