Getting Started with TypeScript
Installing TypeScript
npm install -g typescript
Using tsc
In your code editor create a file logger.ts with the following content:
function log(message) {
console.log(message);
}
log('Hello, world!');
Now you can use a command line to compile your source code to ES5 with tsc tool and run it with node.js:
tsc logger.ts
node logger.js
TypeScript compiler takes logger.ts file, processes it and produces a JavaScript output to logger.js.
At this point, the .js file is ready to be used with an HTML page or executed by node.js.
You should see the following output in the command line:
Hello, world!
Now let's see how type validation works.
Add string type annotation for the log function and call it with a number.
function log(message: string) {
console.log(message);
}
log(0);
If you compile logger.ts once again tsc should produce an error:
tsc logger.ts
> logger.ts(5,5): error TS2345: Argument of type '0' is not assignable to parameter
of type 'string'.
Typings
Linting
TSLint
TSLint checks your TypeScript code for readability, maintainability, and functionality errors.
npm install -g tslint