Steve Fenton

Manipulating variables in JMeter

There are many reasons for manipulating variables in JMeter, especially when you are loading data from a CSV data set config element. You might want to trim a JMeter variable, or grab just a substring.

In all of these cases, your existing knowledge of JavaScript can come to the rescue.

Wherever you were about to use a raw variable, such as ${Example} you can wrap it with a call to the JavaScript processor…


The important thing to remember is that the ${__javaScript( )} will let you drop into JavaScript wherever you can use a variable, so you can easily drop into here to use pretty much any JavaScript stuff that will help you.

You can also store back the result into a different variable, as this example shows – it adds together two variables, trims the string, and stores it in NewVariableName.

${__javaScript("${Prefix} ${SomeValue}".trim(), NewVariableName)}

Written by Steve Fenton on