Merge pull request microsoft#5262 from zhengbli/Fix5127CR

Address code review from 5127

Author: zhengbli

src/compiler/core.ts

@@ -739,13 +739,12 @@ namespace ts {
  export function isSupportedSourceFileName(fileName: string) {
  if (!fileName) { return false; }
 
- let dotIndex = fileName.lastIndexOf(".");
- if (dotIndex < 0) {
- return false;
+ for (let extension of supportedExtensions) {
+ if (fileExtensionIs(fileName, extension)) {
+ return true;
+ }
  }
-
- let extension = fileName.slice(dotIndex, fileName.length);
- return supportedExtensions.indexOf(extension) >= 0;
+ return false;
  }
 
  const extensionsToRemove = [".d.ts", ".ts", ".js", ".tsx", ".jsx"];
@@ -846,7 +845,7 @@ namespace ts {
  export function copyListRemovingItem<T>(item: T, list: T[]) {
  let copiedList: T[] = [];
  for (var i = 0, len = list.length; i < len; i++) {
- if (list[i] != item) {
+ if (list[i] !== item) {
  copiedList.push(list[i]);
  }
  }

src/server/editorServices.ts

@@ -735,7 +735,7 @@ namespace ts.server {
  if (!(--project.projectService.directoryWatchersRefCount[directory])) {
  this.log("Close directory watcher for: " + directory);
  project.projectService.directoryWatchersForTsconfig[directory].close();
- project.projectService.directoryWatchersForTsconfig[directory] = undefined;
+ delete project.projectService.directoryWatchersForTsconfig[directory];
  }
  }
  this.inferredProjects = copyListRemovingItem(project, this.inferredProjects);