{"type":"doc","content":[{"type":"heading","attrs":{"level":1},"content":[{"text":"TypeScript Advanced Types","type":"text"}]},{"type":"heading","attrs":{"level":2},"content":[{"text":"Generics","type":"text"}]},{"type":"codeBlock","attrs":{"language":"typescript"},"content":[{"text":"// Generic function\nfunction identity(arg: T): T {\n return arg;\n}\n\nconst num = identity(42); // Explicit\nconst str = identity('hello'); // Inferred\n\n// Generic with constraints\ninterface Lengthwise {\n length: number;\n}\n\nfunction logLength(arg: T): T {\n console.log(arg.length);\n return arg;\n}\n\nlogLength('hello'); // ✅ string has length\nlogLength([1, 2, 3]); // ✅ array has length\n// logLength(42); // ❌ Error - number doesn't have length\n\n// Generic interface\ninterface ApiResponse {\n data: T;\n status: number;\n message: string;\n}\n\nconst userResponse: ApiResponse = {\n data: { id: 1, name: 'John' },\n status: 200,\n message: 'Success'\n};\n\nconst postsResponse: ApiResponse = {\n data: [{ id: 1, title: 'Post 1' }],\n status: 200,\n message: 'Success'\n};\n\n// Generic class\nclass DataStore {\n private data: T[] = [];\n \n add(item: T): void {\n this.data.push(item);\n }\n \n get(index: number): T | undefined {\n return this.data[index];\n }\n \n getAll(): T[] {\n return this.data;\n }\n \n find(predicate: (item: T) => boolean): T | undefined {\n return this.data.find(predicate);\n }\n}\n\nconst numberStore = new DataStore();\nnumberStore.add(1);\nnumberStore.add(2);\n\nconst userStore = new DataStore();\nuserStore.add({ id: 1, name: 'John' });","type":"text"}]},{"type":"heading","attrs":{"level":2},"content":[{"text":"Utility Types","type":"text"}]},{"type":"codeBlock","attrs":{"language":"typescript"},"content":[{"text":"interface User {\n id: number;\n name: string;\n email: string;\n age: number;\n}\n\n// Partial - all properties optional\ntype PartialUser = Partial;\nconst update: PartialUser = { name: 'Jane' }; // ✅ Only name\n\n// Required - all properties required\ntype RequiredUser = Required;\n\n// Readonly - all properties readonly\ntype ReadonlyUser = Readonly;\nconst user: ReadonlyUser = { id: 1, name: 'John', email: 'john@example.com', age: 30 };\n// user.name = 'Jane'; // ❌ Error\n\n// Pick - pick specific properties\ntype UserPreview = Pick;\nconst preview: UserPreview = { id: 1, name: 'John' };\n\n// Omit - omit specific properties\ntype UserWithoutEmail = Omit;\n\n// Record - object with keys K and values T\ntype Roles = 'admin' | 'user' | 'guest';\ntype Permissions = Record;\n\nconst permissions: Permissions = {\n admin: ['read', 'write', 'delete'],\n user: ['read', 'write'],\n guest: ['read']\n};\n\n// Exclude - exclude types\ntype T1 = Exclude<'a' | 'b' | 'c', 'a'>; // 'b' | 'c'\n\n// Extract - extract types\ntype T2 = Extract<'a' | 'b' | 'c', 'a' | 'b'>; // 'a' | 'b'\n\n// NonNullable - remove null and undefined\ntype T3 = NonNullable; // string\n\n// ReturnType - function return type\nfunction getUser() {\n return { id: 1, name: 'John' };\n}\n\ntype User = ReturnType; // { id: number; name: string }\n\n// Parameters - function parameter types as tuple\ntype Params = Parameters; // []\n\nfunction add(a: number, b: number): number {\n return a + b;\n}\n\ntype AddParams = Parameters; // [number, number]","type":"text"}]},{"type":"heading","attrs":{"level":2},"content":[{"text":"Mapped Types","type":"text"}]},{"type":"codeBlock","attrs":{"language":"typescript"},"content":[{"text":"// Basic mapped type\ntype Readonly = {\n readonly [P in keyof T]: T[P];\n};\n\ntype Optional = {\n [P in keyof T]?: T[P];\n};\n\n// Mapped type with modification\ntype Mutable = {\n -readonly [P in keyof T]: T[P]; // Remove readonly\n};\n\ntype Concrete = {\n [P in keyof T]-?: T[P]; // Remove optional\n};\n\n// Transform property types\ntype Stringify = {\n [P in keyof T]: string;\n};\n\ninterface Numbers {\n a: number;\n b: number;\n}\n\ntype Strings = Stringify; // { a: string; b: string }","type":"text"}]}]}

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Advanced Types (Generics & Utility Types)

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