Simplify selected results table handling

[jcreedcmu]

We don't need to render all tables and use css to hide the ones we
don't currently want to see. Instead have render return the dom that
should be visible given the current state.

[adityasharad]

Please use if instead of ternary so it's easier to read, since the assigned value here has a lot of text!

[jcreedcmu]

I don't care for the fact that

  let val: SomeType | undefined = undefined;
  if (condition)
    val = someComputation();

requires a type annotation, and makes val mutable, when I know that for the rest of the function it should be const. Would you be ok with the idiom condition && someComputation() instead of the ternary, since at least in that case there isn't an undefined stranted after the someComputation()? (I didn't realize until I looked it up just now that react also renders false as nothing, just as it does undefined)

(A utility function renderIf<T>(condition: boolean, value: T): T | undefined could work, though it would have the undesirable consequence that value would be computed regardless of the condition, and

renderIf<T>(condition: boolean, computation: () => T): T | undefined {
  if (condition) return value(); else return undefined;
}

would of course solve that, but that would make you have to throw extra () => in every callsite)

[jcreedcmu]

(@henrymercer agreed in an earlier conversation that it's unfortunate typescript lacks good concrete syntax for conditionals and switch statements as expressions :)

[adityasharad]

Sigh. The minor increase in readability is not worth any of these :) I do appreciate the thorough investigation of options.