in the past I created a site in sharepoint 2013 which I now would like to implement as a Sharepoint Online WebPart. I have been reading a researching a bit, and I've found that WebParts are created using TypeScript. Is that truly the only option I have to build the WebPart? Will all of the functions I used in JavaScript be implementable in TypeScript? Is there a site that you would recommend I use to learn TypeScript? 

Thank you so much in advanced!