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Sunday, November 2, 2014

EcmaScript6 with TypeScript and Grunt.js


ECMAScript 6 is nearly here. In fact I can already taste it and so will you with TypeScript. TypeScript is an open source language and compiler written by Microsoft running on NodeJS. The language is based on the evolving ES6 spec but adds support for types, interfaces that generates JavaScript (ES3 or ES5 dialects based on flag). In fact it's very interesting shift for Microsoft to make something useful for open source community, so before you boo me, have a look at it as it's not so bad.

Introduction


Microsoft has compiled a great video introducing the TypeScript and since one video replaces million words, let's start with it.



Using TypeScript


As TypeScript is built on top of Node.js, installing it will be as easy as breathing. 
npm install -g typescript
And compiling the files is done through the tsc command, however this is no way respectable developers work. We'll be using Grunt.js to compile our TypeScript files during the build phase. Let's start with writing something small using the new syntax. As usual all the accompanying code can be found on article's repository. First we'll create Animal class and extend a Lion from it, overriding it's methods.
class Animal {
    constructor(public eats: string) {}

    eat() {
        console.log('Eating ' + this.eats);
    }

    speak() {
        console.log('Animal speaking');
    }
}

///
class Lion extends Animal {
    constructor() {
        super('meat');
    }

    speak() {
        console.log('Lion roars');
        super.speak();
    }
}
Then check our new classes in the HTML file: 
<!DOCTYPE html>
<html>
<head>
    <script src="src/Animal.js"></script>
    <script src="src/Lion.js"></script>
    <script>
        var lion = new Lion();
        lion.eat();
        lion.speak();
    </script>
</head>
</html>
Pay attention that we reference the js files and not the ts ones. Now let's move to Grunt.js.

TypeScript and Grunt.js


To make both play together nicely, we'll be needing additional package, called grunt-ts. Since we won't be needing it besides development environment, let's use --save-dev flag to mark our intentions. 
npm install grunt-ts --save-dev
Moving on to our gruntfile.js file. I've used as little options as possible to make the example easy to understand. There are a lot of configurations of grunt-ts package, which are thoroughly explained in it's page. 
(function () {
    'use strict';
    module.exports = function(grunt) {
        grunt.initConfig({
            ts: {
                dev: {
                    src: ["src/*.ts"]                
                }
            }
        });

        grunt.loadNpmTasks('grunt-ts');
        grunt.registerTask('default', ['ts:dev']);
    };
}());
Once Grunt task is run, four files will be generated including both JavaScript and Map files of our classes. And of course opening our HTML page, will feed the console with following lines: 
Eating meat               Animal.ts:5
Lion roars                Lion.ts:8
Animal speaking           Animal.ts:9
Pay attention to where Chrome maps the log calls, which is our original ts files. This will come handy in case of debugging your application, which means you don't really need to open the auto-generated JavaScript files.

Besides support in Visual Studio, TypeScript is also supported in WebStorm and SublimeText. Hope you enjoyed the article and next we'll be talking about CoffeeScript.
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