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Question

Can i leran javascript completely bu using Sololearn??
If not,how can i learn??

Answer 1

Short answer no.
Sololearn teaches the basic of all language .
I don't think you can learn any language completely because every language is made based on many subjects but you can learn the advanced level of javascript in w3 school.
Also some reference for you:
https://www.mockplus.com/blog/post/best-places-to-learn-javascript
https://hackernoon.com/10-websites-to-learn-javascript-for-beginners-31e13bbdbb5c