So many answers, so I will be brief.
Java script may serve you 10 years. Then you can join the COBOL experts.
Mathematics was mentioned only by two respondents. I found that being able to use math and statistics well has been the foundation of my career: I started in 1958 and am still consulting - the fields have changed, from missile trajectories, to chemistry of combustion, to compilers, to real-time-data acquistion, to analysis of medical data, to data systems performance, to knowledge extraction, etc. Now I am building models for intellectual property valuation.
Do you want a 10-year future or a 60-year future?
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