A boolean value is one that evaluates to either true or false. The list of false values is indicated below. All other values are true. If a default value is specified in the attribute definition and the attribute is not declared in the HTML or specified as empty (e.g., attribute=”), then the default is used.
Attribute values that evaluate to false:
- unspecified attribute
- blank or empty
- 0 (digit ‘0’)
- f (letter ‘f’, case insensitive)
- false (case insensitive)