[eslint] fix remaining undeclared variables

Author: ljharb

.eslintrc

@@ -1,5 +1,12 @@
 {
     "root": true,
+    "env": {
+        "browser": true,
+        "node": true,
+    },
+    "globals": {
+        "Promise": false,
+    },
     "rules": {
         "indent": ["error", 4],
         "key-spacing": "error",
@@ -8,6 +15,7 @@
             "anonymous": "always",
             "named": "never",
         }],
+        "no-undef": "error",
     },
     "overrides": [
         {
@@ -16,5 +24,11 @@
                 "ecmaVersion": 2017,
             },
         },
+        {
+            "files": ["example/**", "test/**"],
+            "globals": {
+                "g": false,
+            },
+        },
     ],
 }

test/stackTrace.js

@@ -107,7 +107,7 @@ tap.test('preserves stack trace for failed assertions', function (tt) {
     parser.once('assert', function (data) {
         tt.equal(typeof data.diag.at, 'string');
         tt.equal(typeof data.diag.stack, 'string');
-        at = data.diag.at || '';
+        var at = data.diag.at || '';
         stack = data.diag.stack || '';
         tt.ok(/^Error: true should be false(\n    at .+)+/.exec(stack), 'stack should be a stack');
         tt.deepEqual(data, {
@@ -172,7 +172,7 @@ tap.test('preserves stack trace for failed assertions where actual===falsy', fun
     parser.once('assert', function (data) {
         tt.equal(typeof data.diag.at, 'string');
         tt.equal(typeof data.diag.stack, 'string');
-        at = data.diag.at || '';
+        var at = data.diag.at || '';
         stack = data.diag.stack || '';
         tt.ok(/^Error: false should be true(\n    at .+)+/.exec(stack), 'stack should be a stack');
         tt.deepEqual(data, {