My JS engine Porffor can now parse TypeScript, as I added pluggable parser support which includes Babel’s parser (which can parse TS). This itself isn’t that interesting, however I can now use those type annotations as compiler hints to optimize! Basic example leta=1;if(a){console.log(typeofa);} For the above JS, Porffor has to do several checks of the type of a: if (a) { If string, true if non-blank (not '') If undefined, false … If number, true if not zero typeof a If string, 'string'...
