Setup a Typescript project with ESLint, Prettier and VSCode

Jan 02, 2024
Setup a Typescript project with ESLint, Prettier and VSCode
 

1. setup project

//create a new package.json yarn init yarn add typescript --dev //Created a new tsconfig.json npx tsc --init
tsconfig.json
{ "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 '<reference>'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. */ } }
 

2. Eslint configuration

  • vscode setting
    • Install the ESLint VS Code extension.
    • edit your .vscode/settings.json to enable auto-formatting on save
    • { "editor.codeActionsOnSave": { "source.fixAll.eslint": true }, }
  • eslint init
npx eslint --init // Need to install the following packages: // eslint@8.41.0 // Ok to proceed? (y) y // You can also run this command directly using 'npm init @eslint/config'. // Need to install the following packages: // @eslint/create-config@0.4.3 // Ok to proceed? (y) y // ✔ How would you like to use ESLint? · problems // ✔ What type of modules does your project use? · esm // ✔ Which framework does your project use? · none // ✔ Does your project use TypeScript? Yes // ✔ Where does your code run? · browser // ✔ What format do you want your config file to be in? · JSON // Local ESLint installation not found. // The config that you've selected requires the following dependencies: // @typescript-eslint/eslint-plugin@latest @typescript-eslint/parser@latest eslint@latest // ✔ Would you like to install them now? Yes // Successfully created .eslintrc.json file in /Users/maliethy/js_playground/typescript
.eslintrc.json
{ //https://eslint.org/docs/latest/use/configure/ "env": { "browser": true, "es2021": true }, "extends": [ "eslint:recommended", //https://typescript-eslint.io/getting-started/ "plugin:@typescript-eslint/recommended", "plugin:@typescript-eslint/recommended-requiring-type-checking", //https://prettier.io/docs/en/integrating-with-linters.html#recommended-configuration ], "overrides": [ ], "parser": "@typescript-eslint/parser", "parserOptions": { "ecmaVersion": "latest", "sourceType": "module" }, "ignorePatterns": ["dist/", "node_modules/"], "plugins": [ "@typescript-eslint" ], "rules": { } }
 

3. Prettier configuration

  • vscode setting
    • Install the Prettier VS Code extension
    • edit your .vscode/settings.json to enable auto-formatting on save
    • “editor.defaultFormatter”: “esbenp.prettier-vscode”, “editor.formatOnSave”: true
  • Install Prettier
yarn add prettier eslint-config-prettier --dev
  • Add a basic Prettier configuration to share with your team in .prettierrc.json
    • //https://prettier.io/docs/en/options.html { "printWidth": 80, "tabWidth": 2, "useTabs": false, "semi": true, "singleQuote": true, "quoteProps": "consistent", "trailingComma": "es5", "bracketSpacing": true, "arrowParens": "always", "endOfLine": "lf" }
 

4. result

package.json
{ "name": "typescript", "version": "1.0.0", "main": "index.js", "license": "MIT", "dependencies": { "@typescript-eslint/eslint-plugin": "^5.59.7", "@typescript-eslint/parser": "^5.59.7", "eslint": "^8.41.0", "eslint-config-prettier": "^8.8.0", "eslint-plugin-prettier": "^4.2.1", "prettier": "^2.8.8", "typescript": "^5.0.4" } }
  • test
    • make parial.ts file
    • //https://www.typescriptlang.org/docs/handbook/utility-types.html interface Todo { title: string; description: string; } function updateTodo(todo: Todo, fieldsToUpdate: Partial<Todo>) { return { ...todo, ...fieldsToUpdate }; } const todo1 = { title: "organize desk", description: "clear clutter", }; const todo2 = updateTodo(todo1, { description: "throw out trash", });
  • compile ts to js
npx tsc partial.ts
//partial.js var __assign = (this && this.__assign) || function () { __assign = Object.assign || function(t) { for (var s, i = 1, n = arguments.length; i < n; i++) { s = arguments[i]; for (var p in s) if (Object.prototype.hasOwnProperty.call(s, p)) t[p] = s[p]; } return t; }; return __assign.apply(this, arguments); }; function updateTodo(todo, fieldsToUpdate) { return __assign(__assign({}, todo), fieldsToUpdate); } var todo1 = { title: "organize desk", description: "clear clutter", }; var todo2 = updateTodo(todo1, { description: "throw out trash", });
 

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