test: fix RegExp nits

* Remove needless RegExp flag

  In fixed case, `/g` flag is needless in the boolean context.

* Remove needless RegExp capturing

  Use non-capturing grouping or remove capturing completely when:

  * capturing is useless per se, e.g. in test() check;
  * captured groups are not used afterward at all;
  * some of the later captured groups are not used afterward.

* Use test, not match/exec in boolean context

  match() and exec() return a complicated object,
  unneeded in a boolean context.

* Do not needlessly repeat RegExp creation

  This commit takes RegExp creation out of cycles and other repetitions.

  As long as the RegExp does not use /g flag and match indices,
  we are safe here.

  In tests, this fix hardly gives a significant performance gain,
  but it increases clarity and maintainability,
  reassuring some RegExps to be identical.

  RegExp in functions are not taken out of their functions:
  while these functions are called many times
  and their RegExps are recreated with each call,
  the performance gain in test cases
  does not seem to be worth decreasing function self-dependency.

PR-URL: https://github.com/nodejs/node/pull/13770
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

test/parallel/test-internal-errors.js

@@ -5,6 +5,13 @@ const common = require('../common');
 const errors = require('internal/errors');
 const assert = require('assert');
 
+const errMessages = {
+  objectString: /^'object' === 'string'$/,
+  booleanString: /^'boolean' === 'string'$/,
+  numberString: /^'number' === 'string'$/,
+  invalidKey: /^An invalid error message key was used: TEST_FOO_KEY\.$/,
+};
+
 errors.E('TEST_ERROR_1', 'Error for testing purposes: %s');
 errors.E('TEST_ERROR_2', (a, b) => `${a} ${b}`);
 
@@ -43,86 +50,86 @@ assert.throws(
   () => new errors.Error('TEST_FOO_KEY'),
   common.expectsError({
     code: 'ERR_ASSERTION',
-    message: /^An invalid error message key was used: TEST_FOO_KEY\.$/
+    message: errMessages.invalidKey
   }));
 // Calling it twice yields same result (using the key does not create it)
 assert.throws(
   () => new errors.Error('TEST_FOO_KEY'),
   common.expectsError({
     code: 'ERR_ASSERTION',
-    message: /^An invalid error message key was used: TEST_FOO_KEY\.$/
+    message: errMessages.invalidKey
   }));
 assert.throws(
   () => new errors.Error(1),
   common.expectsError({
     code: 'ERR_ASSERTION',
-    message: /^'number' === 'string'$/
+    message: errMessages.numberString
   }));
 assert.throws(
   () => new errors.Error({}),
   common.expectsError({
     code: 'ERR_ASSERTION',
-    message: /^'object' === 'string'$/
+    message: errMessages.objectString
   }));
 assert.throws(
   () => new errors.Error([]),
   common.expectsError({
     code: 'ERR_ASSERTION',
-    message: /^'object' === 'string'$/
+    message: errMessages.objectString
   }));
 assert.throws(
   () => new errors.Error(true),
   common.expectsError({
     code: 'ERR_ASSERTION',
-    message: /^'boolean' === 'string'$/
+    message: errMessages.booleanString
   }));
 assert.throws(
   () => new errors.TypeError(1),
   common.expectsError({
     code: 'ERR_ASSERTION',
-    message: /^'number' === 'string'$/
+    message: errMessages.numberString
   }));
 assert.throws(
   () => new errors.TypeError({}),
   common.expectsError({
     code: 'ERR_ASSERTION',
-    message: /^'object' === 'string'$/
+    message: errMessages.objectString
   }));
 assert.throws(
   () => new errors.TypeError([]),
   common.expectsError({
     code: 'ERR_ASSERTION',
-    message: /^'object' === 'string'$/
+    message: errMessages.objectString
   }));
 assert.throws(
   () => new errors.TypeError(true),
   common.expectsError({
     code: 'ERR_ASSERTION',
-    message: /^'boolean' === 'string'$/
+    message: errMessages.booleanString
   }));
 assert.throws(
   () => new errors.RangeError(1),
   common.expectsError({
     code: 'ERR_ASSERTION',
-    message: /^'number' === 'string'$/
+    message: errMessages.numberString
   }));
 assert.throws(
   () => new errors.RangeError({}),
   common.expectsError({
     code: 'ERR_ASSERTION',
-    message: /^'object' === 'string'$/
+    message: errMessages.objectString
   }));
 assert.throws(
   () => new errors.RangeError([]),
   common.expectsError({
     code: 'ERR_ASSERTION',
-    message: /^'object' === 'string'$/
+    message: errMessages.objectString
   }));
 assert.throws(
   () => new errors.RangeError(true),
   common.expectsError({
     code: 'ERR_ASSERTION',
-    message: /^'boolean' === 'string'$/
+    message: errMessages.booleanString
   }));