About JSR 223 Sampler languages,
I can choose between
javascript (ECMAScript ECMA 262 Edition 51 / Oracle Nashorn 1.8.0_144)
and
js (ECMAScript ECMA 262 Edition 51 / Oracle Nashorn 1.8.0_144)
and
nashorn (ECMAScript ECMA 262 Edition 51 / Oracle Nashorn 1.8.0_144)
What's the difference? it seems that they are the same as JavaScript.
Can I edit the list somehow? remove unused script languages?
(There's also ecmascript language with same properties)
I don't think you will be able to remove entries from there as the drop down is being populated on-the-fly using ScriptEngineManager.getEngineFactories() method which performs discovery of available scripting engines in JMeter Classpath.
With regards which language to use js or javascript the answer is none. It is recommended to use Groovy language for any form of scripting in JMeter tests as well-behaved Groovy scripts can be compiled and cached therefore their performance will be pretty like to "normal" Java code while other scripting languages are being interpreted each time they are being called so when it comes to high loads your JSR223 test element using JavaScript might become a performance bottleneck and ruin your test.
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