diff --git a/Notes.md b/Notes.md index 2b57aa5..ebecc70 100644 --- a/Notes.md +++ b/Notes.md @@ -107,3 +107,146 @@ const list: List = renderList(users); const someUser: User = users[0]; [...] ``` + +# Aufsetzen von Typescript-Projekten + +## Installation + +``` +npm install -g typescript # global +npm install --save-dev typescript # lokal +``` + +## Neues Projekt + +``` +tsc --init +``` + +(Lokal ist der Befehl dann `npx tsc [...]`) + +### Konfiguration +tsconfig.json +```json +{ + "compilerOptions": { + "target": "es2016", + "module": "commonjs", + "esModuleInterop": true, + "forceConsistentCasingInFileNames": true, + "strict": true + } +} +``` + +### Kompilieren + +``` +tsc [] +``` + +## Integration in Webpack-Applikationen + +``` +npm install --save-dev typescript ts-loader +``` +webpack.config.js +``` +module.exports = { + [...] + module: { + rules: [ + { + test: /\.tsx?$/, + use: 'ts-loader', + exclude: /node_modules/, + }, + ], + }, + resolve: { + extensions: ['.tsx', '.ts', '.js'], + }, +}; +``` + +## Nutzung in Vue3 Applikationen +``` +npm install --save-dev typescript +``` +tsconfig.json +```json +{ + "extends": "@vue/tsconfig/tsconfig.json", + [...] +} +``` + +```vue + +``` + +# Migration zu Typescript +Ich habe ein existierendes und großes Javascript Projekt. +Ist der Zug schon abgefahren oder kann ich noch mit Typescript anfangen? + +* Javascript darf Typescript importieren, nicht anders herum +* Wenn man doch Javascript importieren muss, gibt es Umwege + +## Umwege + +Type-Declaration Files + +```js +// maximum-number.js +export function maximumNumber(numbers) { + return Math.max(...numbers); +} +``` + +```ts +// maximum-number.d.ts +export function maximumNumber(numbers: number[]): number; +``` + +* Keine Implementierung +* Kein Type-Checking der Implementierung +* Schnittstellen werden wenigstens typisiert `¯\_(ツ)_/¯` +* Das geht auch mit JS-Libraries + +Unsortiert: +* Types, die man kennen sollte + * Record + * Partial + * Readonly + * union + * intersection + * type vs interface + * typeof + * keyof + * `as` ![img.png](img/trustmebro.png) + + + +* Migration nach Typescript +* Typescript und Vue3 +* Wichtige Typescript Konfigurationen + * strict + * noImplicitAny + * strictNullChecks + * strictPropertyInitialization + * useUnknownInCatchVariables + * noUncheckedIndexAccess +* Typescript-ESLint für noch weniger Fehler + * https://typescript-eslint.io/rules/no-floating-promises/ +* Type-Narrowing + * Duck-Typing + * Monty python? + * If it quacks like a duck... + * ts-auto-guard + + + +# Reminder: Vortrag in der Entwicklung - Donnerstag (den 06.07.) um 12-13 Uhr mit dem Thema **Typescript**. +> Warum hilft uns Typescript unser Frontend robuster zu gestalten und Fehler vorzubeugen? Wie integriere ich Typescript in bestehende Projekte? Und wie sehen die nützlichsten Features aus? + diff --git a/IServ_Logo_White.png b/img/IServ_Logo_White.png similarity index 100% rename from IServ_Logo_White.png rename to img/IServ_Logo_White.png diff --git a/img/busy-doggo.png b/img/busy-doggo.png new file mode 100644 index 0000000..9bb6315 Binary files /dev/null and b/img/busy-doggo.png differ diff --git a/img/self-documenting.png b/img/self-documenting.png new file mode 100644 index 0000000..3486eff Binary files /dev/null and b/img/self-documenting.png differ diff --git a/img/sleep.png b/img/sleep.png new file mode 100644 index 0000000..d4c786a Binary files /dev/null and b/img/sleep.png differ diff --git a/img/trustmebro.png b/img/trustmebro.png new file mode 100644 index 0000000..1ca3ef5 Binary files /dev/null and b/img/trustmebro.png differ diff --git a/img/typescript-integration.png b/img/typescript-integration.png new file mode 100644 index 0000000..d629ab9 Binary files /dev/null and b/img/typescript-integration.png differ diff --git a/img/typescript-migration-1.png b/img/typescript-migration-1.png new file mode 100644 index 0000000..72384fa Binary files /dev/null and b/img/typescript-migration-1.png differ diff --git a/img/typescript-migration-2.png b/img/typescript-migration-2.png new file mode 100644 index 0000000..0c7b9ee Binary files /dev/null and b/img/typescript-migration-2.png differ diff --git a/img/typescript-migration-3.png b/img/typescript-migration-3.png new file mode 100644 index 0000000..9141a07 Binary files /dev/null and b/img/typescript-migration-3.png differ diff --git a/img/typescript-migration-4.png b/img/typescript-migration-4.png new file mode 100644 index 0000000..a8e05aa Binary files /dev/null and b/img/typescript-migration-4.png differ diff --git a/img/webpack-typescript-bundling.png b/img/webpack-typescript-bundling.png new file mode 100644 index 0000000..eeed378 Binary files /dev/null and b/img/webpack-typescript-bundling.png differ diff --git a/live/extension.d.ts b/live/extension.d.ts new file mode 100644 index 0000000..d493611 --- /dev/null +++ b/live/extension.d.ts @@ -0,0 +1 @@ + export function getFileExtension(path: string): string; diff --git a/live/extension.js b/live/extension.js new file mode 100644 index 0000000..7574e67 --- /dev/null +++ b/live/extension.js @@ -0,0 +1,3 @@ +export function getFileExtension(path) { + return path.split(".").slice(-1); +} diff --git a/live/index.js b/live/index.js new file mode 100644 index 0000000..398b6a1 --- /dev/null +++ b/live/index.js @@ -0,0 +1,3 @@ +"use strict"; +let variable = 5; +variable = 10; diff --git a/live/index.ts b/live/index.ts new file mode 100644 index 0000000..68e0379 --- /dev/null +++ b/live/index.ts @@ -0,0 +1,3 @@ +let variable: number = 5; + +variable = 10; diff --git a/live/package-lock.json b/live/package-lock.json new file mode 100644 index 0000000..04667b8 --- /dev/null +++ b/live/package-lock.json @@ -0,0 +1,28 @@ +{ + "name": "live", + "version": "1.0.0", + "lockfileVersion": 3, + "requires": true, + "packages": { + "": { + "name": "live", + "version": "1.0.0", + "license": "ISC", + "dependencies": { + "typescript": "^5.1.6" + } + }, + "node_modules/typescript": { + "version": "5.1.6", + "resolved": "https://registry.npmjs.org/typescript/-/typescript-5.1.6.tgz", + "integrity": "sha512-zaWCozRZ6DLEWAWFrVDz1H6FVXzUSfTy5FUMWsQlU8Ym5JP9eO4xkTIROFCQvhQf61z6O/G6ugw3SgAnvvm+HA==", + "bin": { + "tsc": "bin/tsc", + "tsserver": "bin/tsserver" + }, + "engines": { + "node": ">=14.17" + } + } + } +} diff --git a/live/package.json b/live/package.json new file mode 100644 index 0000000..aea08be --- /dev/null +++ b/live/package.json @@ -0,0 +1,14 @@ +{ + "name": "live", + "version": "1.0.0", + "description": "", + "main": "index.js", + "scripts": { + "test": "echo \"Error: no test specified\" && exit 1" + }, + "author": "", + "license": "ISC", + "dependencies": { + "typescript": "^5.1.6" + } +} diff --git a/live/path.js b/live/path.js new file mode 100644 index 0000000..1b4d42b --- /dev/null +++ b/live/path.js @@ -0,0 +1,4 @@ +"use strict"; +Object.defineProperty(exports, "__esModule", { value: true }); +const extension_js_1 = require("./extension.js"); +console.log((0, extension_js_1.getFileExtension)("some/image.png")); diff --git a/live/path.ts b/live/path.ts new file mode 100644 index 0000000..c6710e2 --- /dev/null +++ b/live/path.ts @@ -0,0 +1,3 @@ +import {getFileExtension} from './extension.js'; +console.log(getFileExtension("some/image.png")); + diff --git a/live/tsconfig.json b/live/tsconfig.json new file mode 100644 index 0000000..e075f97 --- /dev/null +++ b/live/tsconfig.json @@ -0,0 +1,109 @@ +{ + "compilerOptions": { + /* Visit https://aka.ms/tsconfig to read more about this file */ + + /* Projects */ + // "incremental": true, /* Save .tsbuildinfo files to allow for incremental compilation of projects. */ + // "composite": true, /* Enable constraints that allow a TypeScript project to be used with project references. */ + // "tsBuildInfoFile": "./.tsbuildinfo", /* Specify the path to .tsbuildinfo incremental compilation file. */ + // "disableSourceOfProjectReferenceRedirect": true, /* Disable preferring source files instead of declaration files when referencing composite projects. */ + // "disableSolutionSearching": true, /* Opt a project out of multi-project reference checking when editing. */ + // "disableReferencedProjectLoad": true, /* Reduce the number of projects loaded automatically by TypeScript. */ + + /* Language and Environment */ + "target": "es2016", /* Set the JavaScript language version for emitted JavaScript and include compatible library declarations. */ + // "lib": [], /* Specify a set of bundled library declaration files that describe the target runtime environment. */ + // "jsx": "preserve", /* Specify what JSX code is generated. */ + // "experimentalDecorators": true, /* Enable experimental support for legacy experimental decorators. */ + // "emitDecoratorMetadata": true, /* Emit design-type metadata for decorated declarations in source files. */ + // "jsxFactory": "", /* Specify the JSX factory function used when targeting React JSX emit, e.g. 'React.createElement' or 'h'. */ + // "jsxFragmentFactory": "", /* Specify the JSX Fragment reference used for fragments when targeting React JSX emit e.g. 'React.Fragment' or 'Fragment'. */ + // "jsxImportSource": "", /* Specify module specifier used to import the JSX factory functions when using 'jsx: react-jsx*'. */ + // "reactNamespace": "", /* Specify the object invoked for 'createElement'. This only applies when targeting 'react' JSX emit. */ + // "noLib": true, /* Disable including any library files, including the default lib.d.ts. */ + // "useDefineForClassFields": true, /* Emit ECMAScript-standard-compliant class fields. */ + // "moduleDetection": "auto", /* Control what method is used to detect module-format JS files. */ + + /* Modules */ + "module": "commonjs", /* Specify what module code is generated. */ + // "rootDir": "./", /* Specify the root folder within your source files. */ + // "moduleResolution": "node10", /* Specify how TypeScript looks up a file from a given module specifier. */ + // "baseUrl": "./", /* Specify the base directory to resolve non-relative module names. */ + // "paths": {}, /* Specify a set of entries that re-map imports to additional lookup locations. */ + // "rootDirs": [], /* Allow multiple folders to be treated as one when resolving modules. */ + // "typeRoots": [], /* Specify multiple folders that act like './node_modules/@types'. */ + // "types": [], /* Specify type package names to be included without being referenced in a source file. */ + // "allowUmdGlobalAccess": true, /* Allow accessing UMD globals from modules. */ + // "moduleSuffixes": [], /* List of file name suffixes to search when resolving a module. */ + // "allowImportingTsExtensions": true, /* Allow imports to include TypeScript file extensions. Requires '--moduleResolution bundler' and either '--noEmit' or '--emitDeclarationOnly' to be set. */ + // "resolvePackageJsonExports": true, /* Use the package.json 'exports' field when resolving package imports. */ + // "resolvePackageJsonImports": true, /* Use the package.json 'imports' field when resolving imports. */ + // "customConditions": [], /* Conditions to set in addition to the resolver-specific defaults when resolving imports. */ + // "resolveJsonModule": true, /* Enable importing .json files. */ + // "allowArbitraryExtensions": true, /* Enable importing files with any extension, provided a declaration file is present. */ + // "noResolve": true, /* Disallow 'import's, 'require's or ''s from expanding the number of files TypeScript should add to a project. */ + + /* JavaScript Support */ + // "allowJs": true, /* Allow JavaScript files to be a part of your program. Use the 'checkJS' option to get errors from these files. */ + // "checkJs": true, /* Enable error reporting in type-checked JavaScript files. */ + // "maxNodeModuleJsDepth": 1, /* Specify the maximum folder depth used for checking JavaScript files from 'node_modules'. Only applicable with 'allowJs'. */ + + /* Emit */ + // "declaration": true, /* Generate .d.ts files from TypeScript and JavaScript files in your project. */ + // "declarationMap": true, /* Create sourcemaps for d.ts files. */ + // "emitDeclarationOnly": true, /* Only output d.ts files and not JavaScript files. */ + // "sourceMap": true, /* Create source map files for emitted JavaScript files. */ + // "inlineSourceMap": true, /* Include sourcemap files inside the emitted JavaScript. */ + // "outFile": "./", /* Specify a file that bundles all outputs into one JavaScript file. If 'declaration' is true, also designates a file that bundles all .d.ts output. */ + // "outDir": "./", /* Specify an output folder for all emitted files. */ + // "removeComments": true, /* Disable emitting comments. */ + // "noEmit": true, /* Disable emitting files from a compilation. */ + // "importHelpers": true, /* Allow importing helper functions from tslib once per project, instead of including them per-file. */ + // "importsNotUsedAsValues": "remove", /* Specify emit/checking behavior for imports that are only used for types. */ + // "downlevelIteration": true, /* Emit more compliant, but verbose and less performant JavaScript for iteration. */ + // "sourceRoot": "", /* Specify the root path for debuggers to find the reference source code. */ + // "mapRoot": "", /* Specify the location where debugger should locate map files instead of generated locations. */ + // "inlineSources": true, /* Include source code in the sourcemaps inside the emitted JavaScript. */ + // "emitBOM": true, /* Emit a UTF-8 Byte Order Mark (BOM) in the beginning of output files. */ + // "newLine": "crlf", /* Set the newline character for emitting files. */ + // "stripInternal": true, /* Disable emitting declarations that have '@internal' in their JSDoc comments. */ + // "noEmitHelpers": true, /* Disable generating custom helper functions like '__extends' in compiled output. */ + // "noEmitOnError": true, /* Disable emitting files if any type checking errors are reported. */ + // "preserveConstEnums": true, /* Disable erasing 'const enum' declarations in generated code. */ + // "declarationDir": "./", /* Specify the output directory for generated declaration files. */ + // "preserveValueImports": true, /* Preserve unused imported values in the JavaScript output that would otherwise be removed. */ + + /* Interop Constraints */ + // "isolatedModules": true, /* Ensure that each file can be safely transpiled without relying on other imports. */ + // "verbatimModuleSyntax": true, /* Do not transform or elide any imports or exports not marked as type-only, ensuring they are written in the output file's format based on the 'module' setting. */ + // "allowSyntheticDefaultImports": true, /* Allow 'import x from y' when a module doesn't have a default export. */ + "esModuleInterop": true, /* Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility. */ + // "preserveSymlinks": true, /* Disable resolving symlinks to their realpath. This correlates to the same flag in node. */ + "forceConsistentCasingInFileNames": true, /* Ensure that casing is correct in imports. */ + + /* Type Checking */ + "strict": true, /* Enable all strict type-checking options. */ + // "noImplicitAny": true, /* Enable error reporting for expressions and declarations with an implied 'any' type. */ + // "strictNullChecks": true, /* When type checking, take into account 'null' and 'undefined'. */ + // "strictFunctionTypes": true, /* When assigning functions, check to ensure parameters and the return values are subtype-compatible. */ + // "strictBindCallApply": true, /* Check that the arguments for 'bind', 'call', and 'apply' methods match the original function. */ + // "strictPropertyInitialization": true, /* Check for class properties that are declared but not set in the constructor. */ + // "noImplicitThis": true, /* Enable error reporting when 'this' is given the type 'any'. */ + // "useUnknownInCatchVariables": true, /* Default catch clause variables as 'unknown' instead of 'any'. */ + // "alwaysStrict": true, /* Ensure 'use strict' is always emitted. */ + // "noUnusedLocals": true, /* Enable error reporting when local variables aren't read. */ + // "noUnusedParameters": true, /* Raise an error when a function parameter isn't read. */ + // "exactOptionalPropertyTypes": true, /* Interpret optional property types as written, rather than adding 'undefined'. */ + // "noImplicitReturns": true, /* Enable error reporting for codepaths that do not explicitly return in a function. */ + // "noFallthroughCasesInSwitch": true, /* Enable error reporting for fallthrough cases in switch statements. */ + // "noUncheckedIndexedAccess": true, /* Add 'undefined' to a type when accessed using an index. */ + // "noImplicitOverride": true, /* Ensure overriding members in derived classes are marked with an override modifier. */ + // "noPropertyAccessFromIndexSignature": true, /* Enforces using indexed accessors for keys declared using an indexed type. */ + // "allowUnusedLabels": true, /* Disable error reporting for unused labels. */ + // "allowUnreachableCode": true, /* Disable error reporting for unreachable code. */ + + /* Completeness */ + // "skipDefaultLibCheck": true, /* Skip type checking .d.ts files that are included with TypeScript. */ + "skipLibCheck": true /* Skip type checking all .d.ts files. */ + } +} diff --git a/package-lock.json b/package-lock.json index 2ae0390..d2fe61f 100644 --- a/package-lock.json +++ b/package-lock.json @@ -1558,6 +1558,20 @@ "node": "*" } }, + "node_modules/typescript": { + "version": "5.1.6", + "resolved": "https://registry.npmjs.org/typescript/-/typescript-5.1.6.tgz", + "integrity": "sha512-zaWCozRZ6DLEWAWFrVDz1H6FVXzUSfTy5FUMWsQlU8Ym5JP9eO4xkTIROFCQvhQf61z6O/G6ugw3SgAnvvm+HA==", + "optional": true, + "peer": true, + "bin": { + "tsc": "bin/tsc", + "tsserver": "bin/tsserver" + }, + "engines": { + "node": ">=14.17" + } + }, "node_modules/uc.micro": { "version": "1.0.6", "resolved": "https://registry.npmjs.org/uc.micro/-/uc.micro-1.0.6.tgz", @@ -2846,6 +2860,13 @@ "resolved": "https://registry.npmjs.org/traverse/-/traverse-0.3.9.tgz", "integrity": "sha512-iawgk0hLP3SxGKDfnDJf8wTz4p2qImnyihM5Hh/sGvQ3K37dPi/w8sRhdNIxYA1TwFwc5mDhIJq+O0RsvXBKdQ==" }, + "typescript": { + "version": "5.1.6", + "resolved": "https://registry.npmjs.org/typescript/-/typescript-5.1.6.tgz", + "integrity": "sha512-zaWCozRZ6DLEWAWFrVDz1H6FVXzUSfTy5FUMWsQlU8Ym5JP9eO4xkTIROFCQvhQf61z6O/G6ugw3SgAnvvm+HA==", + "optional": true, + "peer": true + }, "uc.micro": { "version": "1.0.6", "resolved": "https://registry.npmjs.org/uc.micro/-/uc.micro-1.0.6.tgz", diff --git a/workshop.md b/workshop.md index a845b47..a5dcbde 100644 --- a/workshop.md +++ b/workshop.md @@ -6,28 +6,375 @@ backgroundColor: #00437a color: #fff --- -![bg left:40% 80% drop-shadow:0,0,0,#fff](IServ_Logo_White.png) +# **Typescript** -# **Marp** +![bg left:40% 80% drop-shadow:0,0,0,#fff](img/IServ_Logo_White.png) -Markdown Presentation Ecosystem - -https://marp.app/ +Endlich ruhig schlafen bei der Frontend-Entwicklung. 😴 --- -# How to write slides +# Was ist Typescript? -Split pages by horizontal ruler (`---`). It's very simple! :satisfied: - -```markdown -# Slide 1 - -foobar +Zusatzinformationen über Typen für Javascript. --- -# Slide 2 +# Fehlt es Javascript an Types? -foobar +```js +var data; // Was darf hier rein? ``` + +--- + +# Fehlt es Javascript an Types? +```js +> var data = "some string"; +> console.log(data); +"some string" +> data = 15; // Why not both? +> console.log(data); +15 + +``` +--- + +# Jetzt mit Types! + +--- + +# Jetzt mit Types! + +```ts +var data: string = "some string"; +console.log(data); +data = 15; // ❌ Error +console.log(data); +``` + +--- + +## Transparenz von Schnittstellen + +Was tut diese Library? +```js +// @iserv/graph.js +export function drawGraph(data, options = {}) { + [... Implementierungsdetails] +} +``` + +--- + +## Transparenz von Schnittstellen + +Was tut diese Library? +```js +// @iserv/graph.js +export function drawGraph(data, options = {}) { + [... Implementierungsdetails] +} +``` + +Besser: Wie benutze ich diese Library? + +--- + +## Transparenz von Schnittstellen + +```js +// @iserv/graph.js +export function drawGraph(data, options = {}) { + [... Implementierungsdetails] +} + +// your-module.js +drawGraph([{ + x: 2, + y: 5, +}, { + x: 3, + y: 7, +}]); +``` + +--- + +## Transparenz von Schnittstellen + +```js +// @iserv/graph.js +export function drawGraph(data, options = {}) { + [... Implementierungsdetails] +} + +// your-module.js +drawGraph([ + 5, + 7 +]); +``` + +--- + +## Transparenz von Schnittstellen + +```js +// @iserv/graph.js +export function drawGraph(data, options = {}) { + [... Implementierungsdetails] +} + +// your-module.js +drawGraph([ + 5, + 7 +], { + start: 0, + stepSize: 1, +}); +``` + +--- + +## Dafür hat man doch JSDoc! + +```js +// @iserv/graph.js +/** + * @typedef {Object} GraphOptions + * @property {HTMLCanvasElement} mount + * @property {number} start + * @property {number} stepSize + * + * @param {GraphOptions} options + */ +export function drawGraph(data, options = {}) { + [...Implementierungsdetail] +} +// your-module.js +drawGraph( + data, + { + mount: document.getElementById('my-canvas'), + start: 2, + stepSize: 1, + }, +) +``` + +--- + +## Warum nicht JSDoc? + +![bg left:50% 100%](img/self-documenting.png) +* JSDoc kann lügen +* Wird nicht automatisch überprüft + +--- + +## Typescript aufsetzen + +![bg left:50% 210%](img/busy-doggo.png) + +* In neuem Projekt +* Integration mit Webpack + +--- + +## Typescript in einem neuen Projekt + +Installieren + +``` +npm install -g typescript # global +npm install --save-dev typescript # lokal +``` + +--- + +## Typescript in einem neuen Projekt + +Neues Projekt + +``` +tsc --init +``` + +* (Lokal ist der Befehl dann `npx tsc [...]`) + +--- + +## Konfiguration + +tsconfig.json +```json +{ + "compilerOptions": { + "target": "es2016", + "module": "commonjs", + "esModuleInterop": true, + "forceConsistentCasingInFileNames": true, + "strict": true, + "skipLibCheck": true + } +} +``` + +--- + +## Kompilieren + +``` +tsc [] +``` + +--- + +## Kompilieren +```ts +// index.ts +let variable: number = 5; + +variable = 10; +``` + +```js +// index.js +"use strict"; +let variable = 5; +variable = 10; +``` +--- +## Integration in Webpack-Projekten + + +--- +## Integration in Webpack-Projekten + +![bg 90%](img/webpack-typescript-bundling.png) + +--- + +## Integration in Webpack-Projekten +``` +npm install --save-dev typescript ts-loader + ^^^^^^^^^ +``` + +--- +## Integration in Webpack-Projekten +```js +// webpack.config.js +module.exports = { + module: { + rules: [ + { + test: /\.tsx?$/, + use: 'ts-loader', + exclude: /node_modules/, + }, + ], + }, + resolve: { + extensions: ['.tsx', '.ts', '.js'], + }, + // [...] +}; +``` +--- + +## Integration in bestehende Projekte + +![bg left:50% 100%](img/typescript-integration.png) + +--- + +## Typescript in Javascript? + +* TS in JS integrieren geht ohne Probleme +* ```ts + // extension.ts + export function getFileExtension(path: string): string { + return path.split(".").slice(-1); + } + // path.js + import {getFileExtension} from './extension.ts'; + console.log(getFileExtension("some/image.png")); + // > "png" + ``` +--- + +## Javascript in Typescript? +* JS in TS integrieren ist schwierig +* ```ts + // extension.js + export function getFileExtension(path) { + return path.split(".").slice(-1); + } + // path.ts + import {getFileExtension} from './extension.ts'; + console.log(getFileExtension("some/image.png")); + ``` + +--- +## Javascript in Typescript +``` +path.ts:1:32 - error TS7016: Could not find a declaration file + for module './extension.js'. +'./extension.js' implicitly has an 'any' type. + +1 import {getFileExtension} from './extension.js'; + ~~~~~~~~~~~~~~~~ +Found 1 error in path.ts:1 +``` + +--- + +![bg 60%](img/typescript-migration-1.png) + +--- + +![bg 60%](img/typescript-migration-2.png) + +--- + +![bg 60%](img/typescript-migration-3.png) + +--- + +## Javascript in Typescript + +Wie damit umgehen? +* Typescript auf weniger strikt stellen + * => Nutzung von Typescript verliert an Wert +* Alle Abhängigkeiten direkt nach Typescript konvertieren + * Nicht immer machbar +* Schnittstellen mit Typen versehen + +--- + +![bg 60%](img/typescript-migration-4.png) + +--- + +## Schnittstellen typisieren + +```ts +// extension.d.ts +export function getFileExtension(path: string): string; +``` + +--- + +## Schnittstellen typisieren + +* Keine Implementierung +* Kein Type-Checking der Implementierung +* Schnittstellen werden wenigstens typisiert `¯\_(ツ)_/¯` +* Das geht auch mit JS-Libraries + +--- + +## Welche Types gibt es?