Convert HEX to RGBA (supports RGB, RRGGBB, RGBA and RRGGBBAA with or without hashtag symbol) // 111 bytes

annotated.js

/*
  Returns a [R,G,B,A] array. [R,G,B] are [0,255] numbers and A is a [0,1] number
*/
function(a){
  return [
          ( v=255,              // We set a variable inside the array to save "var"
            c = "0x"+           // Convert from hexadecimal to decimal
            /\w{8}/.exec(       // We take the first eight alphanumerical characters
              a.replace(        // We convert short hexadecimal to long hexadecimal (RGB(A)->RRGGBB(AA))
                !a[6] && /./g,  // We only convert if it's a short hexadecimal
                '$&$&')         // We double each character
              +"FF"             // We add "FF" as the alpha value for RRGGBB
            )                   // The result of the exec() function will be converted to a string because of the concanation
          )                     // The variable declaration returns the last variable i.e. c
        >>> 24,              // Red part
    	c >> 16 & v,              // Green part
    	c >> 8 & v,               // Blue part
      (c & v)/v                 // Alpha part. We convert it to a [0,1] range
    ]
}

index.js

function(b){return[(v=255,c="0x"+/\w{8}/.exec(b.replace(!b[6]&&/./g,"$&$&")+"FF"))>>>24,c>>16&v,c>>8&v,(c&v)/v]}