TypeScript Strict Mode

1{
2  "compilerOptions": {
3    // Strict type checking
4    "strict": true,
5    "noUncheckedIndexedAccess": true,
6    "exactOptionalPropertyTypes": true,
7    "noPropertyAccessFromIndexSignature": true,
8    "noImplicitReturns": true,
9    "noFallthroughCasesInSwitch": true,
10    "noImplicitOverride": true,
11    "forceConsistentCasingInFileNames": true,
12    "verbatimModuleSyntax": true,
13
14    // Module resolution
15    "target": "ES2022",
16    "module": "ESNext",
17    "moduleResolution": "bundler",
18    "resolveJsonModule": true,
19    "isolatedModules": true,
20    "esModuleInterop": true,
21
22    // Output
23    "noEmit": true,
24    "declaration": true,
25    "declarationMap": true,
26    "sourceMap": true,
27
28    // Paths
29    "baseUrl": ".",
30    "paths": {
31      "@/*": ["./src/*"]
32    },
33
34    // Libraries
35    "lib": ["DOM", "DOM.Iterable", "ES2022"],
36    "jsx": "preserve",
37    "incremental": true,
38
39    // Plugins
40    "plugins": [{ "name": "next" }]
41  },
42  "include": ["next-env.d.ts", "**/*.ts", "**/*.tsx"],
43  "exclude": ["node_modules", "dist", ".next"]
44}
45
46// What each strict flag does:
47// strict: true -> Enables all strict mode flags
48// noUncheckedIndexedAccess -> array[0] is T | undefined
49// exactOptionalPropertyTypes -> { x?: string } is string | undefined, not string | undefined | missing
50// noPropertyAccessFromIndexSignature -> forces obj["key"] over obj.key for index signatures
51// noImplicitReturns -> every code path must return a value
52// noFallthroughCasesInSwitch -> switch cases must break or return
53// noImplicitOverride -> override keyword required for inherited methods
54// verbatimModuleSyntax -> enforces type-only imports with "import type"