Description:-

isDefined( ) :- Evaluates a string value to determine whether the named variable exists.

structKeyExists( ) :- Determines whether a specific key is present in a structure.

isDefined() workflow:-

This function works like this when we pass a variable name/key in this function it searches this key/name in the below scope table order accordingly.

even if we pass the scope name with a variable name/key like this isDefined( "variables.test" ) this will also check in the top scope table order accordingly, and if the variable variables.test key/name is declared in argumentes.test then it will be found in arguments.test variable before variables.test variable.

structKeyExist( ) workflow:-

This function works like this when we pass a variable name/key in this function & also we need to pass the structure/scope in this function as per its arguments method, it only searches this key/name in the specific scope/structure which was passed when it called like structKeyExist( "form", "test" ) or form.keyExist( "test" ). so it will search for fewer scopes.

conclusion:-

by using this structKeyExist( ) function in place of this isDefined( ) the function is far more faster/optimized, it is not only giving some performance but our code is also more readable & maintainable.