inspired me to search for some guidelines and best practices on how to biuld efficient expressions in KNIME. Expressions that could be used for example in ‘Rule Engine’ or ‘String Manipulation’ nodes.
So far, I have found nothing really comprehensive starting with very basic things like operators or logic in building expressions up to more advanced topics (like nested functions). @AlexanderFillbrunn@ScottF@DanielBog would you suggest any guide for this?

@HansS Why the following expression
$Strings$ = “3/4” => $Strings$ = “MEDIUM - 3/4”
is incorrect?

Thank you for mentioning general Javascript course.

As far as the expression is concerned, I’ve got your explanation. But I still don’t understand why there are two lines in the original expression while the line
$Strings$ = “3/4” => “MEDIUM - 3/4”
seems to generate expected outcome.

Remember that a rule engine evaluates one rule at a time, from the top one to the last one; it means that it works like this:

If this is true => Then do this
Else if this is true =>Then do this other thing
Else if this is true =>Then do this thing
...

Going back to your example, what happens if $String$ = “1/2”? Your first condition is not met, so the rule engine evaluates the second rule, which is always true, and will give as a result the current value of $String$ in that cell.

If you are using a rule that only affects/fixes some rows in the table, then the remaining rows need to have a default value otherwise they would be missing in the output table.