Hexadecimal digits

[cmyers]

Again, I'm a JS newbie trying to get by and have to write a function that does the followings:

function isWebColor(v)

where v can be anything. return true if it is a
series of 6 hexadecimal digits (may or may not have #
in front of them). otherwise return false.

So, if v were 123456, then it would be true
if v were 12345, it wouldn't, because there are only 5
digits. Also, since they are hex digits, a-e are
allowed as well, and it doesn't matter if they're
upper case or lower.

v as "#3366AA" would return true.
v as "3366LL" would return false.

Could anyone start me in the right direction to create such a function? Any help would be appreciated.

Thank you.
Cathy

[jeffmott]

function isWebColor(v) {
  // remove optional hash mark
  v = v.replace(/^#?/, "");

  // if not in 3 (ABC) or 6 (AABBCC) digit format, return false
  if (v.length != 3 && v.length != 6)
    return false;

  // if v contains a non-hex character, return false
  if (v.match(/[^0-9a-f]/i))
    return false;

  // passed all tests, return true
  return true;
}

[jeffmott]

Also, here's something else I put together when I misunderstood the question. I changed the function name to reflect its purpose.

function isWebSafeColor(v) {
  v = v.replace(/^#?/, "");

  if (v.length == 3) {
    if (v.match(/[^0369cf]/i))
      return false;
  }

  else if (v.length == 6) {
    if (!v.match(/^([0369cf])\1([0369cf])\2([0369cf])\3$/i))
      return false;
  }

  else return false;

  return true;
}

[Charles]

<script type="text/javascript">
<!--
String.prototype.isWebColor = function () {return /^#?[a-f0-9]{6}$/i.test(this) || /^#?[a-f0-9]{3}$/i.test(this)}

document.write('f00'.isWebColor());
// -->
</script>

1 - Three character colours are also valid. See http://www.w3.org/TR/REC-CSS2/syndata.html#color-units.
2 - This method is sophisticated enough that if you turn this in as homework then your teacher will know that you cheated.

[Dan Drillich]

I slightly modified Charles code to make the pound sign optional -


<script type="text/javascript">
<!--
String.prototype.isWebColor = function () {return /^[#]{0,1}[a-f0-9]{6}$/i.test(this) ||

/^[#]{0,1}[a-f0-9]{3}$/i.test(this)}

document.write('D00'.isWebColor());
// -->
</script>


Cheers,
Dan

[cmyers]

Thanks for all your responses ... I will test them out!

Cathy :)

[Charles]

The pound sign is optional with my method. That's what those question marks are there for.

[Dan Drillich]

You are right Charles - I missed it.