makeHexTransparent

withAlpha.ts

/**
 * Adds transparency to a hex color by appending an alpha value.
 *
 * @param hexColor - A 6-digit hex color string (e.g., '#C1E38C' or 'C1E38C')
 * @param alpha - A number between 0 (fully transparent) and 1 (fully opaque)
 * @returns An 8-digit hex color string with the alpha value appended
 *
 * @example
 * withAlpha('#C1E38C', 0.4)  // Returns '#C1E38C66'
 * withAlpha('#FF0000', 0.5)  // Returns '#FF000080'
 */
export function withAlpha(hexColor: string, alpha: number): string {
  const alphaHex = Math.round(alpha * 255)
    .toString(16)
    .padStart(2, '0')
  return `${hexColor}${alphaHex}`
}