Power Leveling your TypeScript

34c9b2871a5c18c38cc226759e17c538?s=47 Offirmo
November 24, 2016

Power Leveling your TypeScript

One Does Not… write TypeScript so easily! In this Meetup talk, I'll share the tricks and pain points I had to learn in my first 6 months of professional TypeScript. The goal is to spare the reader many hours of Stack Overflow...

34c9b2871a5c18c38cc226759e17c538?s=128

Offirmo

November 24, 2016
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  1. Meetup Paris Typescript – 2016/11/24 - @Dashlane Power Leveling your

    Typescript From beginner to master in no time !
  2. Who am I ? Experienced developer focusing on web for

    5 years @2016 getting things done at Dashlane https://github.com/Offirmo
  3. Welcome to the world of TypeScript www.typescriptlang.org

  4. So you want to become a typescript master ? Prove

    your worth.
  5. “I want code that compile” « As an enterprise web

    application developer, I don't like any scripting or dynamic languages. I like code that compiles (...) TypeScript looks like it will help with some of the problems like having (...) compiling (…) » (somewhere on the net) No. You are asking for a linter. All languages have linters. JS already has an excellent linter: ESLlint TypeScript also has a linter: TSLint They will catch typos and code smells. Use a linter. Now.
  6. “Company BIG™ is using it” • Created by Microsoft •

    Embraced by Google: Angular 2 • Big contributions from Palantir (tslint, blueprint, …) • Webpack is considering a rewrite in typescript Following strong players’ lead may be a good move, But could you make your own opinion ?
  7. Yes or No ? • Editor auto-completion • Types =

    documentation – Collaboration – Faster usage • Types = catching (some) errors – Interfaces – early • Refactoring • ... • New language to learn • NOT trivial • More complicated stack • Typings (find, fix, update…) • Source maps • Can’t use some JS tooling • Bugs • Lagging behind the standard • Static typing sometimes refuses good programs and has to be painfully hacked • ...
  8. Yes or No ? • Editor auto-completion • Types =

    documentation – Collaboration – Faster usage • Types = catching (some) errors – Interfaces – early • Refactoring • ... • New language to learn • NOT trivial • More complicated stack • Typings (find, fix, update…) • Source maps • Can’t use some JS tooling • Bugs • Lagging behind the standard • Static typing sometimes refuses good programs and has to be painfully hacked • ... Short-term Long-term & important
  9. Quick check • Do you work in a team ?

    (3+) • Do you have time right now ? • Is it a long-term project or just a MVP ? • Are you experienced ? • Does your industry need the best ? (ex. Security) • Do you like Typescript ?
  10. Don’t ! • Not a substitute for Unit Tests •

    Not a substitute for Code Reviews • Not a way to go back to your OOP comfort zone – Please learn about functional programming  A Gentle Introduction to Functional JavaScript
  11. Quest cleared ! “Understand why using typescript”

  12. New Quest: “Hello World in Typescript” Do the tutorial: https://www.typescriptlang.org/docs/tutorial.html

  13. Which Typescript ? Go straight at TypeScript 2 (which is

    latest at this time 2016/11/24) npm i –save-dev typescript yarn add –dev typescript
  14. Setup typescript: “tsconfig.json” https://www.typescriptlang.org/docs/handbook/tsconfig-json.html https://www.typescriptlang.org/docs/handbook/compiler-options.html files to compile must be

    declared (more about this later) { "compileOnSave": false, "compilerOptions": { "allowJs": false, "noEmitOnError": true, "noImplicitAny": true, (...) "strictNullChecks": true, "target": "ES6", "module": "ES6", "declaration": true, "sourceMap": true, "outDir": “temp/src.es6" }, "include": [ "src/**/*.ts" ], "exclude": [ "node_modules" ] } new project from scratch or from existing code ? choose the errors to catch ! or else your IDE may launch transpilation ! output control
  15. Quest cleared ! “Hello typescript”

  16. Side-quest: “Know your transpiler” Module ES6 CommonJS AMD UMD SystemJS

    Target ES3 ES5 ES6 You can pick whatever combo (Module + Target)
  17. Execute typescript: node 6 example Target: node v6 99% ES6

    CommonJS tsc target = ES6 module = commonjs Source: Typescript 100% ES6, ?% ES7 ES6 modules
  18. Execute typescript: node 4 example tsc target = ES6 module

    = ES6 Target: node v4 57% ES6 CommonJS tsc target = ES5 module = commonjs Source: Typescript 100% ES6, ?% ES7 ES6 modules Intermediate: ES6 100% ES6 ES6 modules babel babel-preset-es2015- node4 FYI: an alternative stack ☟
  19. New Quest: “Get Things Done in Typescript”

  20. Write types ! • boolean • number • string •

    void • Function • null • undefined Combine them: Interface Person { name: string age: number friends: Person[] } https://www.typescriptlang.org/docs/handbook/basic-types.html
  21. Nullable by default ! interface Foo { name: string age:

    number } interface Foo { name: string age: number | undefined } const x: Foo = { name: undefined, age: undefined } const x: Foo = { name: undefined, age: undefined } "StrictNullChecks": true (tsconfig.json)
  22. enum vs. unions const enum Directions { Up, Down, Left,

    Right } type Directions = 'up' | 'down' | 'left' | 'right' https://www.typescriptlang.org/docs/handbook/enums.html ↓This writing is very convenient
  23. Type vs. Interface • Use interface for grouping • Use

    type to define aliases: type TimeoutMs = number type AdventureModel = JsonSchemaBasedModel<IAdventure>
  24. Modules Detection • If no exports, not a module =

    global variables
  25. Argument destructuring function displayPopup( {onCancel, onConfirm}: {onCancel:()=>void, onConfirm:()=>void} ): void

    { … interface Params { onCancel: () => void onConfirm: () => void } function displayPopup({onCancel, onConfirm}: Params): void { ... https://www.barbarianmeetscoding.com/blog/2016/05/13/argument-destructuring-and-type-annotations-in-typescript/
  26. Hashes and JSON • Hashes can be typed: interface Colors

    {[k: string]: Color } • JSON is a declared type, can be extended: interface JsonSchema extends JSON { title: string additionalProperties: boolean [k: string]: any }
  27. overloading • Not that simple. Better handled in code itself.

    function hello(locutor: string, ...locutors: string[]): void { locutors.unshift(locutor) console.log(`Hello, ${locutors.join(', ')} !`) } hello('typescript world') hello('Joe', 'Jack', 'William', 'Averell')
  28. Type limitations • Object.assign() => use as … • .bind()

    => use ES6
  29. Casting: as X, as any as X • Casting from

    compatible type: let x: any = { name: ‘Lothar’, age: 32 } let user: Person = x as Person • Force casting let x: any = { name: ‘Lothar’ } let user: Person = x as any as Person Don’t overuse it ! Valid use case: mock data in tests
  30. typeof import * as axios from 'axios' interface Dependencies {

    axios: typeof axios } • smell • hack
  31. Can you feel your growth ?

  32. Use a npm module import { debounce } from lodash

    Error ! Typescript CAN NOT consume Javascript (directly)
  33. Boss: “Dark Typings” This boss can never be defeated, only

    repelled :-(
  34. Need to use a “declaration file” (aka “typing”) • A

    special kind of TypeScript file which “annotate” some JS: npm I -D @types/lodash • You NEED them. But may not exist, not be correct, not be up-to-date • @types picked automatically by the compiler (since typescript 2) • Sometimes needed: import * as _ from ‘lodash’ • Write your own: official doc, tutorial (More about this in next talk !) http://stackoverflow.com/questions/38224232/how-to-consume-npm-modules-from-typescript
  35. Boss chased away !

  36. Choose your class to progress further… Back-end (node) Front-end (browser)

    Universal (modules)
  37. Back-end • The simplest ;) • npm I -D @types/node

    • Execute directly: ts-node – With a shebang
  38. Front-end Webpack • typescript loader: ts-loader React • Complete class

    example here • Special linting rules: tslint-react • Typed CSS: typestyle • limitations Angular 2 • (see tutorials)
  39. Execute typescript: browser Target: browser ES5 bundled webpack + ts-loader

    + babel (for ES6 modules) Source: Typescript 100% ES6, ?% ES7 ES6 modules See also awesome-typescript-loader
  40. Execute typescript: browser tsc target = ES6 module = ES6

    +npm/cpx Target: browser ES5 bundled Source: Typescript 100% ES6, ?% ES7 ES6 modules Intermediate: ES6 100% ES6 ES6 modules + css, png... webpack +babel FYI an alternate 2-steps stack which allows to use create-react-app without modification
  41. (npm) npm-run + cpx package.json/scripts "dev1": "tsc --watch", "dev2": "cpx

    'src-ts/**/*.{json,css,png}' src", "dev": "run-p dev1 dev2",
  42. Universal (module) • Generate several versions of your code: node

    stable, ES6, UMD • Generate and expose the typings • NEVER use default exports: babel and typescript won’t work well (see next slide) • Beware of conflicting environments – Node vs. browser on SetTimeout
  43. ES6 exports: no default ! • export default doesn’t play

    well with all platforms • Use only named exports export { Foo, bar } • Named exports are recommended in TypeScript regardless of this issue • Interesting reads: – http://stackoverflow.com/a/38671949/587407 – http://blog.jonasbandi.net/2016/10/myth-of-superset.html#comment-29295611 55 – http://www.jbrantly.com/es6-modules-with-typescript-and-webpack/ – https://github.com/webpack/webpack/issues/706
  44. Real example of a universal TS npm module • https://github.com/Offirmo/hello-world-npm

    • All envs testable with – https://github.com/Offirmo/cross-js-env-tests
  45. Quest achieved

  46. Next quests: “Advanced” • Example of ts tyleguide: typescript coding

    guidelines • TypeScript formatter: tsfmt • Call the typescript compiler from a script: – node-typescript-compiler – Allows to dynamically change config • Useful npm script: syntax watch: "tsc:watch": "npm run tsc -- --watch", • In special cases, you may have to tweak the –lib option: --lib webworker
  47. Final words: Superset ? • Superset of JavaScript ? •

    Comparison : C++ superset of C ? • Superset of WELL-WRITTEN JavaScript ? • http://blog.jonasbandi.net/2016/10/myth-of-superset.html#co mment-2929561155 https://smellegantcode.wordpress.com/2015/07/11/is-typescript-really-a-superset-of-javascript-and-does-it-even-matter/
  48. Thank you

  49. Sources • http://stackoverflow.com/questions/tagged/typescript?sort=frequent&pageSize=50 • https://www.reddit.com/r/typescript/comments/3fp1l2/why_bother_with_typescript/ • http://www.aaron-powell.com/posts/2013-01-07-thoughts-on-typescript.html • https://smellegantcode.wordpress.com/2015/07/11/is-typescript-really-a-superset-of-javascript-and-does-it-even-matter/ •

    https://github.com/Offirmo-team/wiki/wiki/typescript • I was wrong about typescript https://news.ycombinator.com/item?id=11841502 • http://www.jbrantly.com/es6-modules-with-typescript-and-webpack/ • http://www.jbrantly.com/typescript-and-webpack/ •
  50. Resources • http://mogmygear.com/index.php • http://reznik.wikia.com/wiki/Axxa's_Wow_Logo_Creator • http://achievementgen.com/wow/ • http://eu.battle.net/wow/fr/media/wallpapers/