Hex2Rgb.js

hex2rgb.js

function hex (hex){
  if(/^#/.test(hex)){
    hex = hex.slice(1);
  }
  if(hex.length !== 3 && hex.length !== 6 ){
    throw new Error("Invaild hex String");
  }
  
  var digit = hex.split("");
  
  if(digit.length === 3){
    digit = [ digit[0],digit[0],digit[1],digit[1],digit[2],digit[2] ]
  }
  var r = parseInt( [digit[0],digit[1] ].join(""), 16 );
  var g = parseInt( [digit[4],digit[5] ].join(""), 16 );
  var b = parseInt( [digit[2],digit[3] ].join(""), 16 );
  return [r,g,b];
}

test.js

var assert = require('assert');
var hex2rgb = require('./hex2rgb');

describe("hex2rgb",function(){
  it("should throw and error if the arity is incorrect",function(){
    assert.throws(function(){
      hex2rgb("shmee");
    },/Invaild hex String/,"You should read my api docs :/ ");
  });
  it("should return a correct rgb val",function(){
    var rgb = hex2rgb("#fff");
    assert.deepEqual(rgb,[255,255,255],"Your kung fu is strong and white");
  })
});

digit = [ digit[0],digit[0],digit[1],digit[1],digit[2],digit[2] ] (missing ;)
Just saying :)