.js file in place if it’s appropriate. After all, they can co-exist.
If you just want to spike on a single function or maybe a configuration issue across your files, a tried and true, and also highly controversial, suggestion is shifting your types to
any. Just put “any” as your type and slowly backfill once you have your code working.
This is honestly a just plain super useful method of spiking when you’re new to TypeScript, but this method’s got some detractors. If you put off the hard work of rereading TypeScript documentation and training your brain to think about the input types first, then the worry is that you’ll never end up really learning it. Spend some time early on with TypeScript, learning those types and trying to think in a TypeScript way. And then if all else fails and you’re just trying to see if your stupid Redux setup works, shift all the types to
any and just remember to clean up before code review.
You want the computer to carry some of the load for you and getting your tools to play well with TypeScript is a big part of that. If you’re not married to your editor and/or trying to defend it across all comment sections of the Internet, consider VS Code. It’s got a lot of niceties like automatic imports, showing type errors, and autocomplete. Webstorm is also highly recommended. For vim, people here recommend yats when you use TypeScript. For emacs, people here recommend tide and
Really, you should always have a linter in your life. You will not be getting half the benefits of Typescript if you do not have a linter for your project and if your text editor or IDE isn’t set up to pop up with helpful advice. Being able to hover over that offending red line telling me something is wrong is so much easier than spinning up my app only to find out it won’t compile. Right now, Palantir is producing
tslint, but in the future, this should all be a part of
Additionally, when doing fiddly stuff like map-fold-reduce, you can use your linter to tell you what type it expects. Bind an expression to a variable with a deliberately-incorrect type like
void to see what is inferred. Maybe it’ll give you clues to program your way through the collection pipeline chaos.
No really, I do want my debugger, thank you very much TypeScript. There’s a lot of times where TypeScript will actually let you know what’s wrong with your code. But sometimes you just need to stop and debug something! TSLint by default enables
no-console and this will stop your files from compiling. Just turn it off and make sure you don’t commit the change.
For the top of files:
Or just in your config file for the project.
If you’re used to ES5 and you’re now using transpiled ES2018, you can’t test out even a simple ES2018 loop your browser console anymore, but you can iterate through a loop on your perfectly good Node console. This is no surprise for Node programmers, but sometimes Rails-or-Python-stack-heavy folks forget, myself included. Just type
node in your terminal.
Additionally, if you want a TypeScript-specific REPL, there’s ts-node, which lets you try out your TypeScript on the fly. Wut! Amazing, right?
Sometimes it’s hard remembering the types when you’re writing something out. Copy and paste the relevant types into your file and comment it out or just keep that type file open in a different window when you’re writing your implementation.
Sometimes you really do need to tell the compiler that this is the type you think it is.
If this throws an error:
this.span = document.createElement(‘span’);
Then make it this:
this.span = <HTMLSpanElement>document.createElement(‘span’);
What’s wonderful about the TypeScript ecosystem is that you can import types for just about anything, from Mapbox to HTML Elements. If you are working extensively with a library, Definitely Typed almost definitely has a type for that. When you import types remember that you can
extend them if you’re adding on values not originally there.
There’s some admittedly weird syntax for typing destructured assignments. Work on also getting your string literal types and enums in good shape. You’ll use them a lot.
// String literal example
type Easing = “ease-in” | “ease-out”;
Finally, don’t worry. You’ll eventually sort all of your keys alphabetically by default because TypeScript has trained you to do that (we call this machine->human learning). You’ll add in the types in advance and be proactively thinking of your inputs before you write. You’ll change your coding style in small ways and become a better programmer.
And you’ll (mostly) stop using
any when you spike.
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