A function that takes 2 colors as arguments and returns the average color.

averageBetweenTwoHexColors.js

/**
 * 
  Write a function that takes 2 colors as arguments and returns the average color.
  - The parameters will be two 6-digit hexadecimal strings. This does not need to be validated.
  - The return value should be a 6-digit hexadecimal string.
  - The hexadecimal strings represent colors in RGB, much like in CSS.
  - The average color is to be determined by taking the arithmetic mean for each component: red, green and blue.
 **/

/**
 * @author: aneudy abreu(@aneudy1702)
 **/
const averageColorStr = (colorA, colorB) => {
  // get RGB colors
  const [redA, greenA, blueA] = getColorRGBArray(colorA)
  const [redB, greenB, blueB] = getColorRGBArray(colorB)

  // get mean(average) colors
  const meanRed = getMean(redA, redB)
  const meanGreen = getMean(greenA, greenB)
  const meanBlue = getMean(blueA, blueB)

  // get and return hex string
  return getColorHexString(meanRed, meanGreen, meanBlue)

  /**
   * UTILITY METHODS BELLOW
   * */

  /**
   * This methods will transform any hex color into an array
   * of corresponding RGB values.
   * @param color = 6 digit hex color. eg.: ffffff
   * @return Array<Numbers> array of numbers from 0 to 255
   * */
  function getColorRGBArray(color) {
    const pairs = color.toString().match(/.{1,2}/g) || []

    return pairs.map(cHex => (
      parseInt(cHex, 16)
    ))
  }

  /**
   * This method expects N amount parameters that get
   * turn into hex values and returned as a string.
   * @param colorDigits <Array<Integers>> is rested array of parameters
   * containing integers. eg.: getColorHexString(255, 255, 255)
   * @return string containing a hex string. eg.: 'ffffff'
   * */
  function getColorHexString(...colorDigits) {
    return (
      colorDigits.map(c => `${c < 10 ? '0': ''}${c.toString(16)}`).join('')
    )
  }

  /**
   * This methods calculates the mean average of list of numbers.
   * @param numbers<Array<Integers>> is rested array of parameters
   * expected to be integers.
   * @return an integer representing the average of the passed numbers.
   *  */
  function getMean(...numbers) {
    return Math.round(
      numbers.reduce(
        (a, b) => a + b,
        0
      ) /
      numbers.length
    )
  }
}

// this randomColor logic is courtesey of Paul Iris https://www.paulirish.com/2009/random-hex-color-code-snippets/
const randomColor = () => Math.floor(Math.random()*16777215).toString(16)
const colorA = randomColor()
const colorB = randomColor()

// { colorA: '882d6d', colorB: '64a5a9', average: '76698b' }
console.log({
  colorA,
  colorB,
  average: averageColorStr(colorA, colorB)
})