I anticipate that around 150 usages will need to be hand-edited.

"npx eslint src/mongo jstests" finds:

✖ 9777 problems (9777 errors, 0 warnings)
  8754 errors and 0 warnings potentially fixable with the `--fix` option.

I suspect many will be simple replacements, while the remainder will be exceptioned via "eslint-disable-next-line" sort of pragmas.

This will close the gap and allow us to enable "no-var" across all JS code in 10gen/mongo.