add basic typescript page

docs/typescript.md

@@ -0,0 +1,75 @@
+# Typescript
+
+You can write micro:bit programs in a subset of [TypeScript](https://www.typescriptlang.org). 
+TypeScript itself is a superset of JavaScript, and many micro:bit programs,
+especially at the beginner's level, are also just plain JavaScript.
+
+```js
+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 (for example, loops, lexically scoped variables,
+functions, classes, lambdas).
+
+We leverage TypeScript's [type inference](http://www.typescriptlang.org/docs/handbook/type-inference.html) so that
+students need not specify types when clear from context.
+
+## Supported language features
+
+* top-level code in the file: "Hello world!" really is just `basic.showString("Hello world!")`
+* [basic types](http://www.typescriptlang.org/docs/handbook/basic-types.html)
+* [variable declarations](http://www.typescriptlang.org/docs/handbook/variable-declarations.html): `let`, `const`, and `var`
+* [functions](http://www.typescriptlang.org/docs/handbook/functions.html) with lexical scoping and recursion
+
+### User-defined types and modules
+
+* [classes](http://www.typescriptlang.org/docs/handbook/classes.html) with fields, methods and constructors; `new` keyword
+* [enums](http://www.typescriptlang.org/docs/handbook/enums.html)
+* [namespaces](http://www.typescriptlang.org/docs/handbook/namespaces.html)  (a form of modules) 
+
+### Control-flow constructs
+
+* `if ... else if ... else` statements
+* `while` and `do ... while` loops
+* `for(;;)` loops (see below about `for ... in/of`)
+* `break/continue`; also with labeled loops
+* `switch` statement (on numbers only)
+* `debugger` statement for breakpoints
+
+### Expressions
+
+* conditional operator `? :`; lazy boolean operators
+* all arithmetic operators (including bitwise operators); note that in microcontroller targets
+  all arithmetic is performed on integers, also when simulating in the browser
+* strings (with a few common methods)
+* [string templates](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals) (`` `x is ${x}` ``)
+* arrow functions `() => ...`
+* array literals `[1, 2, 3]`
+
+
+## Unsupported language features
+
+We generally stay away from the more dynamic parts of JavaScript. 
+Things you may miss and we may implement:
+
+* exceptions (`throw`, `try ... catch`, `try ... finally`)
+* `for ... of` statements
+* object literals `{ foo: 1, bar: "two" }`
+* method-like properties (get/set accessors)
+* class inheritance
+
+If there is something you'd like to see, please file an issue at [GitHub](http://github.com/microsoft/pxt/issues).

pxtarget.json

@@ -114,8 +114,12 @@
                 "path": "/device"
             },
             {
-                "name": "Blocks Language",
+                "name": "Blocks",
                 "path": "/blocks"
+            },
+            {
+                "name": "TypeScript",
+                "path": "/typescript"
             }
         ],
         "sideDoc": "getting-started"