Merge branch 'master' of https://github.com/Microsoft/pxt-microbit

# Conflicts:
#	package.json

docs/javascript.md

@@ -1,15 +1,57 @@
-# JavaScript
+# JavaScript and TypeScript
 
-If you already know some JavaScript, you might be interested in [the JavaScript and TypeScript languages](/js/lang).
-Otherwise, visit the cards below to starting programming JavaScript with the micro:bit:
+Visit the cards below to starting programming JavaScript and TypeScript with the micro:bit:
 
 ```codecard
 [{
-  "name": "Calling Functions",
-  "url":"/js/call"
+  "name": "Calling",
+  "url":  "/js/call"
 },{
-  "name": "Sequencing Commands",
-  "url":"/js/sequence"
+  "name": "Sequencing",
+  "url":  "/js/sequence"
+},{
+  "name": "Variables",
+  "url":  "/js/variables"
+},{
+  "name": "Operators",
+  "url": "/js/operators"
+},{
+  "name": "Statements",
+  "url": "/js/statements"
+},{
+  "name": "Functions",
+  "url": "/js/functions"
+},{
+  "name": "Types",
+  "url": "/js/types"
+},{
+  "name": "Classes",
+  "url": "/js/classes"
+}]
+```
+
+## More information on TypeScript
+
+You can write micro:bit programs in a subset of [TypeScript](https://www.typescriptlang.org), which is a superset of JavaScript.
+Many micro:bit programs, especially at the beginner's level, are just plain JavaScript. TypeScript introduces class-based 
+object-oriented programming, such as:
+
+```typescript
+class Greeter {
+    greeting: string;
+    constructor(message: string) {
+        this.greeting = message;
+    }
+    greet() {
+        return "Hello, " + this.greeting;
+    }
 }
-]
-```
+
+let greeter = new Greeter("world");
+basic.showString(greeter.greet())
+```
+
+This site is meant for teaching programming first, and JavaScript second. For this
+reason, we have stayed away from concepts that are specific to JavaScript (for
+example, prototype inheritance), and instead focused on ones common to most
+modern programming languages (lexically scoped variables, functions, classes).