Anyone who knows the best articles/sites/etc. to learn about Client Script? There are only few examples in SAs. I spent almost 8 hours and I can't still make my simple client script working.

@Luis have you checked out the developer documentation in the NS

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? You may want to connect with @erictgrubaugh. He's running a few YouTube channels and offers a self study course for SuiteScript. Finally, I do recommend the online self study courses through NetSuite if you have access to a Learning Pass.