diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 6139dda0013..ed9f010c56a 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -661,19 +661,17 @@ namespace ts {
         }
 
         function getSemanticDiagnosticsForFile(sourceFile: SourceFile, cancellationToken: CancellationToken): Diagnostic[] {
-            // For JavaScript files, we don't want to report the normal typescript semantic errors.
-            // Instead, we just report errors for using TypeScript-only constructs from within a
-            // JavaScript file.
-            if (isSourceFileJavaScript(sourceFile)) {
-                return getJavaScriptSemanticDiagnosticsForFile(sourceFile, cancellationToken);
-            }
-
             return runWithCancellationToken(() => {
                 const typeChecker = getDiagnosticsProducingTypeChecker();
 
                 Debug.assert(!!sourceFile.bindDiagnostics);
                 const bindDiagnostics = sourceFile.bindDiagnostics;
-                const checkDiagnostics = typeChecker.getDiagnostics(sourceFile, cancellationToken);
+                // For JavaScript files, we don't want to report the normal typescript semantic errors.
+                // Instead, we just report errors for using TypeScript-only constructs from within a
+                // JavaScript file.
+                const checkDiagnostics = isSourceFileJavaScript(sourceFile) ?
+                    getJavaScriptSemanticDiagnosticsForFile(sourceFile, cancellationToken) :
+                    typeChecker.getDiagnostics(sourceFile, cancellationToken);
                 const fileProcessingDiagnosticsInFile = fileProcessingDiagnostics.getDiagnostics(sourceFile.fileName);
                 const programDiagnosticsInFile = programDiagnostics.getDiagnostics(sourceFile.fileName);
 
@@ -1079,6 +1077,8 @@ namespace ts {
                         const importedFile = findSourceFile(resolution.resolvedFileName, toPath(resolution.resolvedFileName, currentDirectory, getCanonicalFileName), /*isDefaultLib*/ false, file, skipTrivia(file.text, file.imports[i].pos), file.imports[i].end);
 
                         if (importedFile && resolution.isExternalLibraryImport) {
+                            // Since currently irrespective of allowJs, we only look for supportedTypeScript extension external module files,
+                            // this check is ok. Otherwise this would be never true for javascript file
                             if (!isExternalModule(importedFile)) {
                                 const start = getTokenPosOfNode(file.imports[i], file);
                                 fileProcessingDiagnostics.add(createFileDiagnostic(file, start, file.imports[i].end - start, Diagnostics.Exported_external_package_typings_file_0_is_not_a_module_Please_contact_the_package_author_to_update_the_package_definition, importedFile.fileName));
diff --git a/tests/baselines/reference/jsFileCompilationBindDuplicateIdentifier.errors.txt b/tests/baselines/reference/jsFileCompilationBindDuplicateIdentifier.errors.txt
new file mode 100644
index 00000000000..2816eaee8b4
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilationBindDuplicateIdentifier.errors.txt
@@ -0,0 +1,12 @@
+tests/cases/compiler/a.js(1,5): error TS2300: Duplicate identifier 'a'.
+tests/cases/compiler/a.js(2,7): error TS2300: Duplicate identifier 'a'.
+
+
+==== tests/cases/compiler/a.js (2 errors) ====
+    var a = 10;
+        ~
+!!! error TS2300: Duplicate identifier 'a'.
+    class a {
+          ~
+!!! error TS2300: Duplicate identifier 'a'.
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilationBindErrors.errors.txt b/tests/baselines/reference/jsFileCompilationBindErrors.errors.txt
new file mode 100644
index 00000000000..eeae7053333
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilationBindErrors.errors.txt
@@ -0,0 +1,27 @@
+tests/cases/compiler/a.js(1,5): error TS2451: Cannot redeclare block-scoped variable 'C'.
+tests/cases/compiler/a.js(2,5): error TS2451: Cannot redeclare block-scoped variable 'C'.
+tests/cases/compiler/a.js(6,5): error TS7027: Unreachable code detected.
+tests/cases/compiler/a.js(11,9): error TS1100: Invalid use of 'arguments' in strict mode.
+
+
+==== tests/cases/compiler/a.js (4 errors) ====
+    let C = "sss";
+        ~
+!!! error TS2451: Cannot redeclare block-scoped variable 'C'.
+    let C = 0;  // Error: Cannot redeclare block-scoped variable 'C'.
+        ~
+!!! error TS2451: Cannot redeclare block-scoped variable 'C'.
+    
+    function f() {
+        return;
+        return;  // Error: Unreachable code detected.
+        ~~~~~~
+!!! error TS7027: Unreachable code detected.
+    }
+    
+    function b() {
+        "use strict";
+        var arguments = 0;  // Error: Invalid use of 'arguments' in strict mode.
+            ~~~~~~~~~
+!!! error TS1100: Invalid use of 'arguments' in strict mode.
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilationBindErrors.symbols b/tests/baselines/reference/jsFileCompilationBindErrors.symbols
deleted file mode 100644
index 6ad06da1df6..00000000000
--- a/tests/baselines/reference/jsFileCompilationBindErrors.symbols
+++ /dev/null
@@ -1,21 +0,0 @@
-=== tests/cases/compiler/a.js ===
-let C = "sss";
->C : Symbol(C, Decl(a.js, 0, 3))
-
-let C = 0;  // Error: Cannot redeclare block-scoped variable 'C'.
->C : Symbol(C, Decl(a.js, 1, 3))
-
-function f() {
->f : Symbol(f, Decl(a.js, 1, 10))
-
-    return;
-    return;  // Error: Unreachable code detected.
-}
-
-function b() {
->b : Symbol(b, Decl(a.js, 6, 1))
-
-    "use strict";
-    var arguments = 0;  // Error: Invalid use of 'arguments' in strict mode.
->arguments : Symbol(arguments, Decl(a.js, 10, 7))
-}
diff --git a/tests/baselines/reference/jsFileCompilationBindErrors.types b/tests/baselines/reference/jsFileCompilationBindErrors.types
deleted file mode 100644
index 113bcd08bc9..00000000000
--- a/tests/baselines/reference/jsFileCompilationBindErrors.types
+++ /dev/null
@@ -1,26 +0,0 @@
-=== tests/cases/compiler/a.js ===
-let C = "sss";
->C : string
->"sss" : string
-
-let C = 0;  // Error: Cannot redeclare block-scoped variable 'C'.
->C : number
->0 : number
-
-function f() {
->f : () => void
-
-    return;
-    return;  // Error: Unreachable code detected.
-}
-
-function b() {
->b : () => void
-
-    "use strict";
->"use strict" : string
-
-    var arguments = 0;  // Error: Invalid use of 'arguments' in strict mode.
->arguments : number
->0 : number
-}
diff --git a/tests/baselines/reference/jsFileCompilationBindMultipleDefaultExports.errors.txt b/tests/baselines/reference/jsFileCompilationBindMultipleDefaultExports.errors.txt
new file mode 100644
index 00000000000..733f66922ab
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilationBindMultipleDefaultExports.errors.txt
@@ -0,0 +1,18 @@
+tests/cases/compiler/a.js(1,22): error TS2528: A module cannot have multiple default exports.
+tests/cases/compiler/a.js(3,1): error TS2528: A module cannot have multiple default exports.
+tests/cases/compiler/a.js(3,1): error TS8003: 'export=' can only be used in a .ts file.
+tests/cases/compiler/a.js(3,16): error TS1109: Expression expected.
+
+
+==== tests/cases/compiler/a.js (4 errors) ====
+    export default class a {
+                         ~
+!!! error TS2528: A module cannot have multiple default exports.
+    }
+    export default var a = 10;
+    ~~~~~~~~~~~~~~
+!!! error TS2528: A module cannot have multiple default exports.
+    ~~~~~~~~~~~~~~
+!!! error TS8003: 'export=' can only be used in a .ts file.
+                   ~~~
+!!! error TS1109: Expression expected.
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilationBindReachabilityErrors.errors.txt b/tests/baselines/reference/jsFileCompilationBindReachabilityErrors.errors.txt
new file mode 100644
index 00000000000..a883e66e607
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilationBindReachabilityErrors.errors.txt
@@ -0,0 +1,31 @@
+tests/cases/compiler/a.js(3,9): error TS7029: Fallthrough case in switch.
+tests/cases/compiler/a.js(16,5): error TS7027: Unreachable code detected.
+tests/cases/compiler/a.js(19,1): error TS7028: Unused label.
+
+
+==== tests/cases/compiler/a.js (3 errors) ====
+    function foo(a, b) {
+        switch (a) {
+            case 10:
+            ~~~~
+!!! error TS7029: Fallthrough case in switch.
+                if (b) {
+                    return b;
+                }
+            case 20:
+                return a;
+        }
+    }
+    
+    function bar() {
+        return x;
+        function bar2() {
+        }
+        var x = 10; // error
+        ~~~
+!!! error TS7027: Unreachable code detected.
+    }
+    
+    label1:  var x2 = 10;
+    ~~~~~~
+!!! error TS7028: Unused label.
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilationBindStrictModeErrors.errors.txt b/tests/baselines/reference/jsFileCompilationBindStrictModeErrors.errors.txt
new file mode 100644
index 00000000000..65dffb5a08e
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilationBindStrictModeErrors.errors.txt
@@ -0,0 +1,81 @@
+tests/cases/compiler/a.js(3,5): error TS2300: Duplicate identifier 'a'.
+tests/cases/compiler/a.js(5,5): error TS1117: An object literal cannot have multiple properties with the same name in strict mode.
+tests/cases/compiler/a.js(5,5): error TS2300: Duplicate identifier 'a'.
+tests/cases/compiler/a.js(7,5): error TS1212: Identifier expected. 'let' is a reserved word in strict mode
+tests/cases/compiler/a.js(8,8): error TS1102: 'delete' cannot be called on an identifier in strict mode.
+tests/cases/compiler/a.js(10,10): error TS1100: Invalid use of 'eval' in strict mode.
+tests/cases/compiler/a.js(12,10): error TS1100: Invalid use of 'arguments' in strict mode.
+tests/cases/compiler/a.js(15,1): error TS1101: 'with' statements are not allowed in strict mode.
+tests/cases/compiler/b.js(3,7): error TS1210: Invalid use of 'eval'. Class definitions are automatically in strict mode.
+tests/cases/compiler/b.js(6,13): error TS1213: Identifier expected. 'let' is a reserved word in strict mode. Class definitions are automatically in strict mode.
+tests/cases/compiler/c.js(1,12): error TS1214: Identifier expected. 'let' is a reserved word in strict mode. Modules are automatically in strict mode.
+tests/cases/compiler/c.js(2,5): error TS1215: Invalid use of 'eval'. Modules are automatically in strict mode.
+tests/cases/compiler/d.js(2,9): error TS1121: Octal literals are not allowed in strict mode.
+tests/cases/compiler/d.js(2,11): error TS1005: ',' expected.
+
+
+==== tests/cases/compiler/a.js (8 errors) ====
+    "use strict";
+    var a = {
+        a: "hello", // error
+        ~
+!!! error TS2300: Duplicate identifier 'a'.
+        b: 10,
+        a: 10 // error
+        ~
+!!! error TS1117: An object literal cannot have multiple properties with the same name in strict mode.
+        ~
+!!! error TS2300: Duplicate identifier 'a'.
+    };
+    var let = 10; // error
+        ~~~
+!!! error TS1212: Identifier expected. 'let' is a reserved word in strict mode
+    delete a; // error
+           ~
+!!! error TS1102: 'delete' cannot be called on an identifier in strict mode.
+    try {
+    } catch (eval) { // error
+             ~~~~
+!!! error TS1100: Invalid use of 'eval' in strict mode.
+    }
+    function arguments() { // error
+             ~~~~~~~~~
+!!! error TS1100: Invalid use of 'arguments' in strict mode.
+    }
+    
+    with (a) {
+    ~~~~
+!!! error TS1101: 'with' statements are not allowed in strict mode.
+        b = 10;
+    }
+    
+==== tests/cases/compiler/b.js (2 errors) ====
+    // this is not in strict mode but class definitions are always in strict mode
+    class c {
+        a(eval) { //error
+          ~~~~
+!!! error TS1210: Invalid use of 'eval'. Class definitions are automatically in strict mode.
+        }
+        method() {
+            var let = 10; // error
+                ~~~
+!!! error TS1213: Identifier expected. 'let' is a reserved word in strict mode. Class definitions are automatically in strict mode.
+        }
+    }
+    
+==== tests/cases/compiler/c.js (2 errors) ====
+    export var let = 10; // external modules are automatically in strict mode
+               ~~~
+!!! error TS1214: Identifier expected. 'let' is a reserved word in strict mode. Modules are automatically in strict mode.
+    var eval = function () {
+        ~~~~
+!!! error TS1215: Invalid use of 'eval'. Modules are automatically in strict mode.
+    };
+    
+==== tests/cases/compiler/d.js (2 errors) ====
+    "use strict";
+    var x = 009; // error
+            ~~
+!!! error TS1121: Octal literals are not allowed in strict mode.
+              ~
+!!! error TS1005: ',' expected.
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilationExportAssignmentSyntax.errors.txt b/tests/baselines/reference/jsFileCompilationExportAssignmentSyntax.errors.txt
index f537941c55c..3be5f99823a 100644
--- a/tests/baselines/reference/jsFileCompilationExportAssignmentSyntax.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationExportAssignmentSyntax.errors.txt
@@ -1,9 +1,12 @@
 error TS5055: Cannot write file 'tests/cases/compiler/a.js' because it would overwrite input file.
+tests/cases/compiler/a.js(1,1): error TS1148: Cannot compile modules unless the '--module' flag is provided.
 tests/cases/compiler/a.js(1,1): error TS8003: 'export=' can only be used in a .ts file.
 
 
 !!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' because it would overwrite input file.
-==== tests/cases/compiler/a.js (1 errors) ====
+==== tests/cases/compiler/a.js (2 errors) ====
     export = b;
     ~~~~~~~~~~~
+!!! error TS1148: Cannot compile modules unless the '--module' flag is provided.
+    ~~~~~~~~~~~
 !!! error TS8003: 'export=' can only be used in a .ts file.
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilationExternalPackageError.errors.txt b/tests/baselines/reference/jsFileCompilationExternalPackageError.errors.txt
new file mode 100644
index 00000000000..58111c777f1
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilationExternalPackageError.errors.txt
@@ -0,0 +1,19 @@
+tests/cases/compiler/moduleA/a.js(2,17): error TS2656: Exported external package typings file 'tests/cases/compiler/node_modules/b.ts' is not a module. Please contact the package author to update the package definition.
+
+
+==== tests/cases/compiler/moduleA/a.js (1 errors) ====
+    
+    import {a} from "b";
+                    ~~~
+!!! error TS2656: Exported external package typings file 'b.ts' is not a module. Please contact the package author to update the package definition.
+    a++;
+    import {c} from "c";
+    c++;
+    
+==== tests/cases/compiler/node_modules/b.ts (0 errors) ====
+    var a = 10;
+    
+==== tests/cases/compiler/node_modules/c.js (0 errors) ====
+    exports.a = 10;
+    c = 10;
+    
\ No newline at end of file
diff --git a/tests/cases/compiler/jsFileCompilationBindDuplicateIdentifier.ts b/tests/cases/compiler/jsFileCompilationBindDuplicateIdentifier.ts
new file mode 100644
index 00000000000..3433adc17d5
--- /dev/null
+++ b/tests/cases/compiler/jsFileCompilationBindDuplicateIdentifier.ts
@@ -0,0 +1,6 @@
+// @allowJs: true
+// @noEmit: true
+// @filename: a.js
+var a = 10;
+class a {
+}
\ No newline at end of file
diff --git a/tests/cases/compiler/jsFileCompilationBindMultipleDefaultExports.ts b/tests/cases/compiler/jsFileCompilationBindMultipleDefaultExports.ts
new file mode 100644
index 00000000000..32a9e77fcc7
--- /dev/null
+++ b/tests/cases/compiler/jsFileCompilationBindMultipleDefaultExports.ts
@@ -0,0 +1,7 @@
+// @allowJs: true
+// @noEmit: true
+// @filename: a.js
+// @target: es6
+export default class a {
+}
+export default var a = 10;
\ No newline at end of file
diff --git a/tests/cases/compiler/jsFileCompilationBindReachabilityErrors.ts b/tests/cases/compiler/jsFileCompilationBindReachabilityErrors.ts
new file mode 100644
index 00000000000..b95f85c2139
--- /dev/null
+++ b/tests/cases/compiler/jsFileCompilationBindReachabilityErrors.ts
@@ -0,0 +1,23 @@
+// @allowJs: true
+// @noEmit: true
+// @filename: a.js
+// @noFallthroughCasesInSwitch: true
+function foo(a, b) {
+    switch (a) {
+        case 10:
+            if (b) {
+                return b;
+            }
+        case 20:
+            return a;
+    }
+}
+
+function bar() {
+    return x;
+    function bar2() {
+    }
+    var x = 10; // error
+}
+
+label1:  var x2 = 10;
\ No newline at end of file
diff --git a/tests/cases/compiler/jsFileCompilationBindStrictModeErrors.ts b/tests/cases/compiler/jsFileCompilationBindStrictModeErrors.ts
new file mode 100644
index 00000000000..30b43b1990e
--- /dev/null
+++ b/tests/cases/compiler/jsFileCompilationBindStrictModeErrors.ts
@@ -0,0 +1,40 @@
+// @allowJs: true
+// @noEmit: true
+// @filename: a.js
+// @target: es6
+"use strict";
+var a = {
+    a: "hello", // error
+    b: 10,
+    a: 10 // error
+};
+var let = 10; // error
+delete a; // error
+try {
+} catch (eval) { // error
+}
+function arguments() { // error
+}
+
+with (a) {
+    b = 10;
+}
+
+// @filename: b.js
+// this is not in strict mode but class definitions are always in strict mode
+class c {
+    a(eval) { //error
+    }
+    method() {
+        var let = 10; // error
+    }
+}
+
+// @filename: c.js
+export var let = 10; // external modules are automatically in strict mode
+var eval = function () {
+};
+
+//@filename: d.js
+"use strict";
+var x = 009; // error
\ No newline at end of file
diff --git a/tests/cases/compiler/jsFileCompilationExternalPackageError.ts b/tests/cases/compiler/jsFileCompilationExternalPackageError.ts
new file mode 100644
index 00000000000..cb9d32adb82
--- /dev/null
+++ b/tests/cases/compiler/jsFileCompilationExternalPackageError.ts
@@ -0,0 +1,16 @@
+// @allowJs: true
+// @noEmit: true
+// @module: commonjs
+
+// @filename: moduleA/a.js
+import {a} from "b";
+a++;
+import {c} from "c";
+c++;
+
+// @filename: node_modules/b.ts
+var a = 10;
+
+// @filename: node_modules/c.js
+exports.a = 10;
+c = 10;
diff --git a/tests/cases/fourslash/getJavaScriptSemanticDiagnostics2.ts b/tests/cases/fourslash/getJavaScriptSemanticDiagnostics2.ts
index 9ab29b41798..58c02dae183 100644
--- a/tests/cases/fourslash/getJavaScriptSemanticDiagnostics2.ts
+++ b/tests/cases/fourslash/getJavaScriptSemanticDiagnostics2.ts
@@ -11,5 +11,12 @@ verify.getSemanticDiagnostics(`[
     "length": 11,
     "category": "error",
     "code": 8003
+  },
+  {
+    "message": "Cannot compile modules unless the '--module' flag is provided.",
+    "start": 0,
+    "length": 11,
+    "category": "error",
+    "code": 1148
   }
 ]`);
\ No newline at end of file