added detectStrictMode-module

Author: Johannes

lib/detectStrictMode.js

@@ -0,0 +1,5 @@
+function detectStrictMode(src) {
+    return (/^\s*"use strict";/g).test(src);
+}
+
+module.exports = detectStrictMode;

test/detectStrictMode.test.js

@@ -0,0 +1,13 @@
+var expect = require("expect.js"),
+    detectStrictMode = require("../lib/detectStrictMode.js");
+
+describe("detectStrictMode", function () {
+    it("should detect \"use strict\"; at the beginning of a string and ignore all whitespace before", function () {
+        expect(detectStrictMode('"use strict";')).to.be(true);
+        expect(detectStrictMode('      "use strict";')).to.be(true);
+        expect(detectStrictMode('  \n "use strict";')).to.be(true);
+    });
+    it("should not detect \"use strict\"; if it occurs in some nested function", function () {
+        expect(detectStrictMode('function () {"use strict";}')).to.be(false);
+    });
+});

test/testModules/strictModule.js

@@ -0,0 +1,7 @@
+"use strict"; // run code in ES5 strict mode
+
+function doSomethingUnstrict() {
+    var caller = arguments.callee.caller;   // this should throw an error as a proof that strict mode is on
+}
+
+exports.doSomethingUnstrict = doSomethingUnstrict;