Find the best contrast color to overlay onto given color.

calculateColorContrast.js

export function getContrastYIQ(color, colorType){
  let r, g, b;
  const start = color.indexOf('#') === 0 ? 1 : 0;

  if (colorType === 'hex') {
    r = parseInt(color.substr(start, 2), 16);
    g = parseInt(color.substr(start + 2, 2), 16);
    b = parseInt(color.substr(start + 4, 2), 16);
  } else if (colorType == 'rgb') {
    [r, g, b] = color.slice(4, -1).split(',').map(str => +str);
  } else {
    throw Error(`Incorrect color type given. Expected 'hex' or 'rgb', but saw '${colorType}'`);
  }

  const yiq = ((r * 299) + (g * 587) + (b * 114)) / 1000;
  return (yiq >= 128) ? 'black' : 'white';
}