v6.x backport: test: refactor several parallel/test-timer tests

[BethGriggs]

Change var to const/let. Simplify test-timers-uncaught-exception.

PR-URL: #10524
Reviewed-By: James M Snell jasnell@gmail.com
Reviewed-By: Gibson Fahnestock gibfahn@gmail.com
Reviewed-By: Jeremiah Senkpiel fishrock123@rocketmail.com

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

Affected core subsystem(s)

Test

/cc @gibfahn

[sam-github]

ci: https://ci.nodejs.org/job/node-test-pull-request/7381/

[lpinca]

@BethGriggs I took the liberty of updating PR title.

[MylesBorins]

so it seems like the work from this PR ended up getting wrapped into another backport that has already landed. Thanks for putting the time into this @BethGriggs, fun to run into you in the PR tracker 😄

[gibfahn]

@MylesBorins Is that true? The changes to the first file were just var->const, and they went into a different PR, but the changes to the other files don't seem to have gone into v6.x-staging, e.g. test-timers-uncaught-exception.js on v6.x-staging.

e.g. this diff:

-console.error('set first timer');
-setTimeout(function() {
-  console.error('first timer');
-  timer1++;
-  throw new Error('BAM!');
-}, 100);
+setTimeout(common.mustCall(function() {
+  throw new Error(errorMsg);
+}), 1);

isn't in test-timers-uncaught-exception.js#L10-L15.

[gibfahn]

CI: https://ci.nodejs.org/job/node-test-commit/9193/

[gibfahn]

CI 2: https://ci.nodejs.org/job/node-test-commit/9241/

[MylesBorins]

landed in 9218661