Change markdownlint-browser.js TypeScript configuration to generate code for "es2015" ("es6") from the default of "es3" so that generated code for for..of will behave correctly, revert previous workaround for same.

demo/tsconfig.json

@@ -1,7 +1,8 @@
 {
   "compilerOptions": {
     "allowJs": true,
-    "outDir": "unused"
+    "outDir": "unused",
+    "target": "es2015"
   },
   "include": [
     "../lib/*.js"

helpers/helpers.js

@@ -609,13 +609,13 @@ module.exports.codeBlockAndSpanRanges = (params, lineMetadata) => {
         tokenLines.join("\n"),
         (code, lineIndex, columnIndex) => {
           const codeLines = code.split(newLineRe);
-          codeLines.forEach((line, i) => {
+          for (const [ i, line ] of codeLines.entries()) {
             exclusions.push([
               token.lineNumber - 1 + lineIndex + i,
               i ? 0 : columnIndex,
               line.length
             ]);
-          });
+          }
         }
       );
     }