Syntax
exists_expression ::= 'exists:' expression
Description
Exists expressions test for the existence of paths. An exists expression returns true when the path expressions following its expression returns a value and it is not undefined. It is false when the path expression cannot locate an object or if it evaluates to undefined.
Note: some parts extracted from Zope Page Templates Reference.
Differences with ZPT
In ZPT if an expression evaluates to undefined exists returns true; ZPT-JS returns false.
Examples
Testing for the existence of a property in an object:
<div data-condition="not: exists: myObject/name">
Name not set!
</div>
Note: some parts extracted from Zope Page Templates Reference.