convert RGB to HEX

annotated.js

function(
  a, // red, as a number from 0 to 255
  b, // green, as a number from 0 to 255
  c  // blue, as a number from 0 to 255
){
  return "#" +   // return a number sign, and
  (              // combine the octets into a 32-bit integer as: [1][a][b][c]    
    (            // operator precedence is (+) > (<<) > (|)
      256  // [1][0]
      + a  // [1][a] 
      << 8 // [1][a][0]
      | b  // [1][a][b]
    )
    << 8   // [1][a][b][0]
    | c    // [1][a][b][c]
  )
  .toString(16)  // then serialize to a hex string, and
  .slice(1)      // remove the 1 to get the number with 0s intact.
}

index.js

function(a,b,c){return"#"+((256+a<<8|b)<<8|c).toString(16).slice(1)}

LICENSE.txt

            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
                    Version 2, December 2004

 Copyright (C) 2011 Jed Schmidt <http://jed.is>

 Everyone is permitted to copy and distribute verbatim or modified
 copies of this license document, and changing it is allowed as long
 as the name is changed.

            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

  0. You just DO WHAT THE FUCK YOU WANT TO.

package.json

{
  "name": "rgb2hex",

  "description": "Converts RGB colors to a hexadecimal string.",

  "keywords": [
    "color",
    "css",
    "hex",
    "rgb" 
  ]
}