Friday, July 27, 2018

Do Things Right with TypeScript

A collection of pointers for the present and future.

Print the whole error


`tsc --noErrorTruncation`

Why tsconfig.json is hard


tsconfig.json is important, because the TS compiler does way more, way more flexibly, than the Java compiler does. It's both a transpiler and a typechecker.

What kind of JS do you want outputted? Choose your level of ECMAScript compatibility (as ancient as ES3 or as modern as ESnext) and also your module system compatibility (commonjs, amd, or several more).

What will be magically be available in your runtime? Bring in the type declarations for these things (such as the DOM) with the `"lib": ["DOM"]` compiler option, or in `"types": ["@types/node"]` (node module globals like `__filename`, or node built-ins like `fs`).

Also choose how stringent the typechecking is, with "strict" and its various suboptions.

Choose where your input files are, and where your output files go.

Choose what to output: only JS? sourcemaps? type declarations? type declaration maps?  ... and for those maps, choose relative paths to the source.

The good news is: even if compilation has errors, tsc will output JS. So you can test even when tricky compile errors that you can't figure out plague you.

Iterate through objects and arrays


There exists both `for (const a of array)` and a similar construct which shall not be named but contains the work `in` instead of `of`. Do not use that one.

To iterate through an array: for (const a of array) { ... }

... ok I can't stand it anymore I'm moving this post to Medium. Google clearly does not care about this platform, it may go away like Google Reader, and it is super painful to put code here.

https://medium.com/@jessitron/do-things-right-with-typescript-7a3ad7371387

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