true if the specified key value exists in the map; otherwise false.

Called

Use this method to guard calls to the Map.lookup method. If the Map.lookup method does not find the value it is looking for, it throws an exception.

The following example checks whether a particular style exists in a map of styles in a style sheet. If it does, a new name is substituted for the body style.

static void renameStyle(Map stylesheet, str fromName, str toName)
{
    str body;
    ;
    if (stylesheet.exists(fromName))
    {
        body = stylesheet.lookup (fromName);
        stylesheet.remove (fromName);
        stylesheet.insert (toName, body);
    }
    else
    {
        info (fromName);
    }
}