I think Observable has been a greater productivity boost than Typescript. Partial recompilation of running programs with production debugging via Chrome dev tools. Its the modern Smalltalk. Its a great fit for iterative development like #Dataviz, but I think it also has legs beyond.
It took me a minute to get used to Observable's workflow, but the thoughtful integration of key libraries, speed of execution, and general usefulness have made it an indispensable tool for my data visualization and creative coding needs.