I don't know what you wanna do with JS, is it frontend dev? cuz I have never heard that JS and Data Science go together, I heard about R & Python going with DS (I don't know a lot about DS).
This ES6 course is really good:
JS is been used for DS lately. I would recommend getting up-to-speed with it. However, it is always nice to have Python as your backup language for DS/ML.
Ah... js is eating the world man, with no typing :D
The only downside is that you have to know your way around CPU intensive tasks. The biggest issue with JS is that the Math engine is not as powerful/accurate on floating-point operations.
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