TypeScript Tricks I wish I knew when I learned TypeScript

• TypeScript

  1,302 97,832 9.9 TypeScript

  TypeScript is a superset of JavaScript that compiles to clean JavaScript output.

  

  Short comment about the 'unknown' type: TypeScript 4.4 had me learning about it very recently, because 'unknown' has been made the default type in 'catch (error)' clauses [0]. So most of our code in 'catch' blocks suddenly didn't compile any more after an unsuspecting update of the TS version.

  Which is a good thing, because in reviewing those I found several places where incorrect assumptions were being made about the type of error that would be caught.

  (side note: TypeScript does not follow SemVer; they just promise to avoid breaking changes in Patch updates, but don't promise anything won't break in Minor updates [1])

  [0]: https://devblogs.microsoft.com/typescript/announcing-typescr...

  [1]: https://github.com/microsoft/TypeScript/issues/14116#issueco...

• lodash

  187 58,812 5.2 JavaScript

  A modern JavaScript utility library delivering modularity, performance, & extras.

  

  Probably best to just lift one off of a major library like Lodash, they're well tested and efficient (no need to actually use the library):

  https://github.com/lodash/lodash/blob/master/isObject.js

  But depends on your needs, and you can also attach a typeguard to it.

• SurveyJS

  surveyjs.io

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• @sindresorhus/is

  1 1,615 6.9 TypeScript

  Type check values (by sindresorhus)

  I really like this package, because it not only uses the method you mentioned for checking types, but is written in TS, so you get the type checking feedback.

  https://github.com/sindresorhus/is

• typing-euler

  1 0 10.0 TypeScript

  Discontinued Typing Euler because values are code smells

• graphql-js

  26 19,905 7.4 TypeScript

  A reference implementation of GraphQL for JavaScript

  

  > I have only seen null vs undefined lead to 2 things in my experience: mistakes and bikeshedding.

  I disagree, though I think the implementation leaves something to be desired. Primarily, I think there is fundamentally a difference between the value of obj.bar in the following examples that is useful to differentiate between:

  { foo: 'hello' }

  { foo: 'hello', bar: null }

  For example, GraphQL makes specific use of this when dealing with input types for mutations: null essentially means "delete this field" while unset means "don't change it".

  There is a very good discussion on this topic here, https://github.com/graphql/graphql-js/issues/133 , which goes into the rationale behind it, how it's supported in languages that do NOT differentiate between null and undefined, and how some folks changed their minds on the issue.

• milewski-ctfp-pdf

  75 10,733 5.3 TeX

  Bartosz Milewski's 'Category Theory for Programmers' unofficial PDF and LaTeX source

  You don't need a PhD, you just need the first few chapters of [Category Theory for Programmers](https://github.com/hmemcpy/milewski-ctfp-pdf) :)

• ts-sql

  28 3,114 0.0 TypeScript

  A SQL database implemented purely in TypeScript type annotations.

  

• InfluxDB

  www.influxdata.com

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• json-parser-in-typescript-very-bad-idea-please-dont-use

  4 431 0.0 TypeScript

  JSON Parser written entirely in TypeScript's type system

• json-parser-in-typescript-ver

  2 - -

• typanion

  3 247 4.6 TypeScript

  Static and runtime type assertion library with no dependencies

• Yup

  113 22,166 7.1 TypeScript

  Dead simple Object schema validation

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