Get SID from object-type, get object-type from SID

Get SID from object-type
var sid = objtype.sid

Get object-type from sid
var obktype = this.runtime.getObjectTypeBySid(sid);

It will check the object-types list to find the matched target. Keeping the index of the matched target might increase the performance.
var objtypes = this.runtime.types_by_index;
var t = objtypes[index];
if ((t != null) && (t.sid === sid))   // find the target
    return t;
var i, len=objtypes.length;
for (i=0; i<len; i++)
{
    t = objtypes[i];
    if (t.sid === sid)      // find the target
    {
        index = i;          // save the index
        return t;
    }
}

Reference