diff --git a/src/harness/harnessLanguageService.ts b/src/harness/harnessLanguageService.ts
index 682496442e9..08c74e695be 100644
--- a/src/harness/harnessLanguageService.ts
+++ b/src/harness/harnessLanguageService.ts
@@ -135,7 +135,7 @@ namespace Harness.LanguageService {
 
         public getFilenames(): string[] {
             const fileNames: string[] = [];
-            this.virtualFileSystem.getAllFileEntries().forEach((virtualEntry) => {
+            ts.forEach(this.virtualFileSystem.getAllFileEntries(), (virtualEntry) => {
                 const scriptInfo = virtualEntry.content;
                 if (scriptInfo.isRootFile) {
                     // only include root files here
diff --git a/src/harness/virtualFileSystem.ts b/src/harness/virtualFileSystem.ts
index 5a89efea7fa..2a46bf4c3fe 100644
--- a/src/harness/virtualFileSystem.ts
+++ b/src/harness/virtualFileSystem.ts
@@ -158,6 +158,11 @@ namespace Utils {
             return directory;
         }
 
+        /**
+         * Reads the directory at the given path and retrieves a list of file names and a list
+         * of directory names within it. Suitable for use with ts.matchFiles()
+         * @param path  The path to the directory to be read
+         */
         getAccessibleFileSystemEntries(path: string) {
             const entry = this.traversePath(path);
             if (entry && entry.isDirectory()) {
@@ -176,8 +181,8 @@ namespace Utils {
             return fileEntries;
 
             function getFilesRecursive(dir: VirtualDirectory<T>, result: VirtualFile<T>[]) {
-                dir.getFiles().forEach((e) => result.push(e));
-                dir.getDirectories().forEach((subDir) => getFilesRecursive(subDir, result));
+                ts.forEach(dir.getFiles(), (e) => result.push(e));
+                ts.forEach(dir.getDirectories(), (subDir) => getFilesRecursive(subDir, result));
             }
         }
 
diff --git a/src/services/services.ts b/src/services/services.ts
index 04c435f1339..b7e79473fcd 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -1947,8 +1947,15 @@ namespace ts {
         sourceMapText?: string;
     }
 
-
+    // Matches the beginning of a triple slash directive
     const tripleSlashDirectivePrefixRegex = /^\/\/\/\s*</;
+
+    /**
+     * Matches a triple slash reference directive with an incomplete string literal for its path. Used
+     * to determine if the caret is currently within the string literal and capture the literal fragment
+     * for completions.
+     * For example, this matches /// <reference path="fragment
+     */
     const tripleSlashDirectiveFragmentRegex = /^\/\/\/\s*<reference\s+path\s*=\s*(?:'|")([^'"]+)$/;
 
     let commandLineOptionsStringToEnum: CommandLineOptionOfCustomType[];
@@ -4386,7 +4393,7 @@ namespace ts {
                 if (directoryProbablyExists(baseDir, host)) {
                     // Enumerate the available files
                     const files = host.readDirectory(baseDir, extensions, /*exclude*/undefined, /*include*/["./*"]);
-                    files.forEach((f) => {
+                    ts.forEach(files, (f) => {
                         const fName = includeExtensions ? getBaseFileName(f) : removeFileExtension(getBaseFileName(f));
 
                         if (startsWith(fName, toComplete)) {
@@ -4402,7 +4409,7 @@ namespace ts {
                     // If possible, get folder completion as well
                     if (host.getDirectories) {
                         const directories = host.getDirectories(baseDir);
-                        directories.forEach((d) => {
+                        ts.forEach(directories, (d) => {
                             const dName = getBaseFileName(removeTrailingDirectorySeparator(d));
 
                             if (startsWith(dName, toComplete)) {
@@ -4471,7 +4478,7 @@ namespace ts {
                 // Check for node_modules. We only offer completions for modules that are listed in the
                 // package.json for a project for efficiency and to ensure that the completion list is
                 // not polluted with sub-dependencies
-                findPackageJsons(scriptPath).forEach((packageJson) => {
+                ts.forEach(findPackageJsons(scriptPath), (packageJson) => {
                     const package = tryReadingPackageJson(packageJson);
                     if (!package) {
                         return;
@@ -4487,13 +4494,13 @@ namespace ts {
                         addPotentialPackageNames(package.devDependencies, moduleNameFragment, foundModuleNames);
                     }
 
-                    foundModuleNames.forEach((moduleName) => {
+                    ts.forEach(foundModuleNames, (moduleName) => {
                         if (isNestedModule && moduleName === moduleNameFragment) {
                             const moduleDir = combinePaths(nodeModulesDir, moduleName);
                             if (directoryProbablyExists(moduleDir, host)) {
                                 const nestedFiles = host.readDirectory(moduleDir, supportedTypeScriptExtensions, /*exclude*/undefined, /*include*/["./*"]);
 
-                                nestedFiles.forEach((f) => {
+                                ts.forEach(nestedFiles, (f) => {
                                     const nestedModule = removeFileExtension(getBaseFileName(f));
                                     nonRelativeModules.push(nestedModule);
                                 });