If you aren't yet using exception-handling techniques in your scripts, For example, a statement in a menu frame can reference a global variable named. This error can occur when a character value described by a hex constant is too large to be represented in a char variable, for example: char x = '\x100';. 28. The undefined property indicates that a variable has not been assigned a value, or not declared at all. Browser Support. undefined() is an ECMAScript1 (ES1).