npm i hex-color-opacity
const opacity = require('hex-color-opacity') opacity('#FFFFFF', 0.5)
Adding opacity to hexadecimal color values
To add opacity to a hex color simply pass the color value (this includes the # character) and the desired opacity as a number value between 0 and 1 to the opacity function. The resulting hex value is returned. Support for 3 value hex colors is provided out of the box. All hex values are returned in upper case.
opacity('#FFF', 0.5) // #FFFFFF80
Contributors are welcome, feel free to submit a new pull request to help improve hex-color-opacity.