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# VBScript IsNull Function * * Complete VBScript Reference Manual](#) * * * The IsNull function returns a Boolean value indicating whether the specified expression contains invalid data (Null). It returns True if the expression is Null; otherwise, it returns False. ### Syntax IsNull(expression) | Parameter | Description | | :--- | :--- | | expression | Required. An expression. | ## Example ## Example Dim x document.write(IsNull(x) & "
") x=10 document.write(IsNull(x) & "
") x=Empty document.write(IsNull(x) & "
") x=Null document.write(IsNull(x)) The output of the above example is: False False False True [Try it »](#) * * Complete VBScript Reference Manual](#)