Comment by IshKebab

I like Vega, but I hate that it is not very efficient. It uses array-of-structs which is not efficient in JavaScript. For example to create a heat map you have an object for every single point. Also there does not seem to be a way to do proper heat maps at all (i.e. an interpolated image), only a grid of squares.

Finally I'm not really sure of the point of being declarative if it only supports JavaScript anyway. Maybe they plan a WASM implementation?