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-rw-r--r--typescript.html.markdown77
1 files changed, 44 insertions, 33 deletions
diff --git a/typescript.html.markdown b/typescript.html.markdown
index 47e41405..ef37182d 100644
--- a/typescript.html.markdown
+++ b/typescript.html.markdown
@@ -9,29 +9,38 @@ TypeScript is a language that aims at easing development of large scale applicat
TypeScript adds common concepts such as classes, modules, interfaces, generics and (optional) static typing to JavaScript.
It is a superset of JavaScript: all JavaScript code is valid TypeScript code so it can be added seamlessly to any project. The TypeScript compiler emits JavaScript.
-This article will focus only on TypeScript extra syntax, as opposed to [JavaScript] (../javascript/).
+This article will focus only on TypeScript extra syntax, as opposed to [JavaScript](javascript.html.markdown).
To test TypeScript's compiler, head to the [Playground] (http://www.typescriptlang.org/Playground) where you will be able to type code, have auto completion and directly see the emitted JavaScript.
-```js
+```ts
// There are 3 basic types in TypeScript
-var isDone: boolean = false;
-var lines: number = 42;
-var name: string = "Anders";
+let isDone: boolean = false;
+let lines: number = 42;
+let name: string = "Anders";
+
+// But you can omit the type annotation if the variables are derived from explicit literals
+let isDone = false;
+let lines = 42;
+let name = "Anders";
// When it's impossible to know, there is the "Any" type
-var notSure: any = 4;
+let notSure: any = 4;
notSure = "maybe a string instead";
notSure = false; // okay, definitely a boolean
+// Use const keyword for constant variables
+const numLivesForCat = 9;
+numLivesForCat = 1; // Error
+
// For collections, there are typed arrays and generic arrays
-var list: number[] = [1, 2, 3];
+let list: number[] = [1, 2, 3];
// Alternatively, using the generic array type
-var list: Array<number> = [1, 2, 3];
+let list: Array<number> = [1, 2, 3];
// For enumerations:
-enum Color {Red, Green, Blue};
-var c: Color = Color.Green;
+enum Color { Red, Green, Blue };
+let c: Color = Color.Green;
// Lastly, "void" is used in the special case of a function returning nothing
function bigHorribleAlert(): void {
@@ -43,14 +52,16 @@ function bigHorribleAlert(): void {
// The following are equivalent, the same signature will be infered by the
// compiler, and same JavaScript will be emitted
-var f1 = function(i: number): number { return i * i; }
-// Return type inferred
-var f2 = function(i: number) { return i * i; }
-var f3 = (i: number): number => { return i * i; }
+let f1 = function (i: number): number { return i * i; }
// Return type inferred
-var f4 = (i: number) => { return i * i; }
-// Return type inferred, one-liner means no return keyword needed
-var f5 = (i: number) => i * i;
+let f2 = function (i: number) { return i * i; }
+// "Fat arrow" syntax
+let f3 = (i: number): number => { return i * i; }
+// "Fat arrow" syntax with return type inferred
+let f4 = (i: number) => { return i * i; }
+// "Fat arrow" syntax with return type inferred, braceless means no return
+// keyword needed
+let f5 = (i: number) => i * i;
// Interfaces are structural, anything that has the properties is compliant with
// the interface
@@ -64,19 +75,19 @@ interface Person {
// Object that implements the "Person" interface
// Can be treated as a Person since it has the name and move properties
-var p: Person = { name: "Bobby", move: () => {} };
+let p: Person = { name: "Bobby", move: () => { } };
// Objects that have the optional property:
-var validPerson: Person = { name: "Bobby", age: 42, move: () => {} };
+let validPerson: Person = { name: "Bobby", age: 42, move: () => { } };
// Is not a person because age is not a number
-var invalidPerson: Person = { name: "Bobby", age: true };
+let invalidPerson: Person = { name: "Bobby", age: true };
// Interfaces can also describe a function type
interface SearchFunc {
(source: string, subString: string): boolean;
}
// Only the parameters' types are important, names are not important.
-var mySearch: SearchFunc;
-mySearch = function(src: string, sub: string) {
+let mySearch: SearchFunc;
+mySearch = function (src: string, sub: string) {
return src.search(sub) != -1;
}
@@ -102,8 +113,8 @@ class Point {
static origin = new Point(0, 0);
}
-var p1 = new Point(10 ,20);
-var p2 = new Point(25); //y will be 0
+let p1 = new Point(10, 20);
+let p2 = new Point(25); //y will be 0
// Inheritance
class Point3D extends Point {
@@ -113,7 +124,7 @@ class Point3D extends Point {
// Overwrite
dist() {
- var d = super.dist();
+ let d = super.dist();
return Math.sqrt(d * d + this.z * this.z);
}
}
@@ -129,12 +140,12 @@ module Geometry {
}
}
-var s1 = new Geometry.Square(5);
+let s1 = new Geometry.Square(5);
// Local alias for referencing a module
import G = Geometry;
-var s2 = new G.Square(10);
+let s2 = new G.Square(10);
// Generics
// Classes
@@ -150,28 +161,28 @@ interface Pair<T> {
}
// And functions
-var pairToTuple = function<T>(p: Pair<T>) {
+let pairToTuple = function <T>(p: Pair<T>) {
return new Tuple(p.item1, p.item2);
};
-var tuple = pairToTuple({ item1:"hello", item2:"world"});
+let tuple = pairToTuple({ item1: "hello", item2: "world" });
// Including references to a definition file:
/// <reference path="jquery.d.ts" />
// Template Strings (strings that use backticks)
// String Interpolation with Template Strings
-var name = 'Tyrone';
-var greeting = `Hi ${name}, how are you?`
+let name = 'Tyrone';
+let greeting = `Hi ${name}, how are you?`
// Multiline Strings with Template Strings
-var multiline = `This is an example
+let multiline = `This is an example
of a multiline string`;
```
## Further Reading
* [TypeScript Official website] (http://www.typescriptlang.org/)
- * [TypeScript language specifications (pdf)] (http://go.microsoft.com/fwlink/?LinkId=267238)
+ * [TypeScript language specifications] (https://github.com/Microsoft/TypeScript/blob/master/doc/spec.md)
* [Anders Hejlsberg - Introducing TypeScript on Channel 9] (http://channel9.msdn.com/posts/Anders-Hejlsberg-Introducing-TypeScript)
* [Source Code on GitHub] (https://github.com/Microsoft/TypeScript)
* [Definitely Typed - repository for type definitions] (http://definitelytyped.org/)