Evaluates a string value to determine whether the variable named in it exists.

isDefined(variable_name) → returns boolean

Argument Reference

variable_name string

A string expression containing the name of a variable to check the existence of. Only simple dotted notation is supported (for example myVar, arguments.myArg, myStruct.key). Square bracket notation to reference array elements or struct keys is not supported.

Links more information about isDefined

Sample code invoking the isDefined function

Checking for the existence of a form variable.

<cfif isDefined("form.submit")>...</cfif>

Beware of scope evaluation order when checking for an unscoped variable name. = "" ; = ""; writeoutput("Is 'foo' defined? " & isDefined("foo")); writeoutput(isDefined("foo") ? " (" & foo & ")" : "");

Expected Result: Is 'foo' defined? YES (

Potentially unexpected behavior when checking for a dot-notation variable containing a scope name.

local["form.submit"] = "local['form.submit']" ; form.submit = "form.submit"; writeoutput("Is 'form.submit' defined?" & isDefined("form.submit")); writeoutput(isDefined("form.submit") ? " (" & form.submit & ")" : ""); writeoutput("<br>"); writeoutput("Is 'submit' defined? " & isDefined("submit")); writeoutput(isDefined("submit") ? " (" & submit & ")" : "");

Expected Result: Is 'form.submit' defined? YES (local['form.submit']) Is 'submit' defined? YES(form.submit)

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