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About TypeScript

I didn’t touch TypeScript once in the last 3 years. I stopped using it when I changed my job, from Angular 4 back to jQuery, AngularJS, and forth to VueJS.

  • Did I miss it? Not once.
  • Did I like it when I had to use it? I did.

But now my opinion on TypeScript is that it works like a self fulfilling prophecy. You think you need some control on the types of values you pass around in your application, and, in fact, as soon as you write a line of TypeScript, the linter first, and the compiler later, will immediately spot so many type errors. If you think about how many lines you wrote in JavaScript in the past, without any sort of type checking, they must have been all wrong!

Well, not really. The simplicity and strength of JavaScript is it lacks type checking. I wrote millions of lines of JavaScript, and not many of them with errors. I already know how to protect me from most of them. While developing, the JavaScript linter and the JavaScript test runner will immediately spot whatever I mistook. But also TypeScript needs a linter and a test runner, so that they do not represent a price for the lack of type checking.

While running… well, while running TypeScript is JavaScript and loses any notion of type. Surprising, but true. TypeScript only checks types at compilation time. You should validate whatever data enter into and exit from your code. For example, using Ajv to validate the JSON schemas of the responses you get for requests issued to API endpoints. Again, you need data validation in any case, so it’s not a price for the lack of type checking.

In the end, it seems to me that the benefits of TypeScript are less relevant than the drawbacks. Which is essentially one: development slowness, for having to get types right, when wrong types are hardly so subtle errors that you wouldn’t detect otherwise.

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Ship

Recently, I recovered an old piece of JavaScript code I wrote more than 10 years ago.

It’s a simple game where you control a (conceptual) spaceship.

You are under a continuous attack of red balls, which you seem to attract.

You get a chance to survive yet a bit more, by shooting at them before they hit you.

But don’t hit blue balls before they reach you, otherwise you won’t recover some much needed energy.

You shoot with the SPACE bar and aim with the mouse pointer.

Enjoy

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How to ´Promise.all´ the values of a JS hash

For doing something like this:

var hash = { key1: value1, key2: promise2, ... };
Promise.all(hash).then(hash => ...);

I wrote this little function:

  function promiseAll(hash) {
    const keys = Object.keys(hash);
    const values = keys.map(key => hash[key]);
    return Promise.all(values).then(resolved_values => {
      const resolved_hash = {};
      keys.forEach((key, index) => {
        resolved_hash[key] = resolved_values[index];
      });
      return resolved_hash;
    });
  }

which allows you to do this:

var hash = { key1: value1, key2: promise2, ... };
promiseAll(hash).then(hash => ...);