Question

I understand how to match it but I don’t know the criteria for example, Email matcher would use: /^([A-Za-z0-9_\-\.])+\@([A-Za-z0-9_\-\.])+\.([A-Za-z]{2,4})$/ but I need to know what a steam id would use.

Demo Steam ID: STEAM_0:1:20206720

Could someone give me a criteria for STEAM IDs?

EDIT:
I’m using the regex expression provided by pimvdb, but it still replys that a steam id(STEAM_0:1:20206720) is incorrect.

My code is below:

function verifySteamID(){
    var elem = document.getElementById('item_name');
    var emailExp = /^STEAM_[0-5]:[01]:\d+$/;
    if(elem.value.match(emailExp)){
        document.getElementById("error").setAttribute("class", "hidden");
        return true;
    }else{
        document.getElementById("error").setAttribute("class", "unhidden");
        elem.focus();
        return false;
    }
    }

Which is called by:

<input type="submit" value="Donate" id="donatebtn" onclick="return verifySteamID()" />

Answer 1

According to http://developer.valvesoftware.com/wiki/SteamID#Format it might be something along the lines of:

/^STEAM_[0-5]:[01]:\d+$/

^...$ is just so that the exact string must match.

STEAM_ is the prefix.

After the prefix there should be one number ranging from 0 to 5.

Then a : followed by either a 0 or 1.

Then another : followed by the account number.