{"id":12630,"date":"2026-02-25T03:37:28","date_gmt":"2026-02-25T03:37:28","guid":{"rendered":"https:\/\/withcode.tech\/media\/?p=12630"},"modified":"2026-07-01T15:29:05","modified_gmt":"2026-07-01T15:29:05","slug":"typescript-type-safety-benefits","status":"publish","type":"post","link":"https:\/\/withcode.tech\/media\/typescript-type-safety-benefits\/","title":{"rendered":"\u3010\u5b8c\u5168\u30ac\u30a4\u30c9\u3011TypeScript\u306e\u578b\u5b89\u5168\u6027\u304cWeb\u5236\u4f5c\u306b\u3082\u305f\u3089\u30595\u3064\u306e\u30e1\u30ea\u30c3\u30c8\uff5c\u5c0e\u5165\u304b\u3089\u5b9f\u8df5\u307e\u3067\u5fb9\u5e95\u89e3\u8aac"},"content":{"rendered":"
\"\"\u751f\u5f92<\/span><\/div>
\n

TypeScript\u3063\u3066\u96e3\u3057\u305d\u3046\u3067\u3059\u3051\u3069\u3001JavaScript\u3067\u5341\u5206\u3058\u3083\u306a\u3044\u3093\u3067\u3059\u304b\uff1f<\/strong><\/p>\n<\/span><\/span><\/span><\/div><\/div><\/div><\/div>\n\n

\"\"\u30da\u30f3\u535a\u58eb<\/span><\/div>
\n

\u3088\u30fc\u304f\u805e\u304f\u3093\u3060\u305e\uff01TypeScript\u306e\u578b\u5b89\u5168\u6027\u306f\u3001\u30d0\u30b0\u3092\u672a\u7136\u306b\u9632\u304e\u3001\u958b\u767a\u52b9\u7387\u3092\u5287\u7684\u306b\u5411\u4e0a\u3055\u305b\u308b\u3093\u3058\u3083\u3002\u4eca\u65e5\u306fWeb\u5236\u4f5c\u3067TypeScript\u3092\u4f7f\u3046\u30e1\u30ea\u30c3\u30c8\u3092\u8a73\u3057\u304f\u89e3\u8aac\u3059\u308b\u305e\u3044\uff01<\/strong><\/p>\n<\/span><\/span><\/span><\/div><\/div><\/div><\/div>\n\n\n

\n

\u3053\u306e\u8a18\u4e8b\u3067\u308f\u304b\u308b\u3053\u3068<\/h2>\n
    \n
  • TypeScript\u306e\u578b\u5b89\u5168\u6027\u3068\u306f\u4f55\u304b\u3001JavaScript\u3068\u306e\u9055\u3044\u3092\u30b3\u30fc\u30c9\u4f8b\u3067\u7406\u89e3\u3059\u308b<\/li>\n
  • Web\u5236\u4f5c\u3067TypeScript\u3092\u4f7f\u30465\u3064\u306e\u5177\u4f53\u7684\u306a\u30e1\u30ea\u30c3\u30c8<\/li>\n
  • \u65b0\u898f\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\u30fb\u65e2\u5b58\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\u53cc\u65b9\u3078\u306eTypeScript\u5c0e\u5165\u624b\u9806<\/li>\n
  • React\u30fbNext.js\u30fbVue 3\u3067\u306eTypeScript\u5b9f\u8df5\u30b3\u30fc\u30c9<\/li>\n
  • TypeScript\u5c0e\u5165\u306e\u5224\u65ad\u57fa\u6e96\uff08\u5411\u304f\u5834\u5408\u30fb\u5411\u304b\u306a\u3044\u5834\u5408\uff09<\/li>\n<\/ul>\n<\/div><\/div>\n\n\n\n

    Web\u5236\u4f5c\u306e\u73fe\u5834\u3067\u306fJavaScript\u304c\u9577\u5e74\u4f7f\u308f\u308c\u3066\u304d\u307e\u3057\u305f\u304c\u3001\u8fd1\u5e74TypeScript<\/strong>\u306e\u63a1\u7528\u304c\u6025\u901f\u306b\u5e83\u307e\u3063\u3066\u3044\u307e\u3059\u3002\u578b\u5b89\u5168\u6027\uff08Type Safety\uff09\u306b\u3088\u308a\u3001\u30b3\u30f3\u30d1\u30a4\u30eb\u6642\u306b\u30d0\u30b0\u3092\u767a\u898b\u3067\u304d\u3001\u30c1\u30fc\u30e0\u958b\u767a\u3067\u306e\u54c1\u8cea\u3068\u52b9\u7387\u304c\u5287\u7684\u306b\u5411\u4e0a<\/strong>\u3057\u307e\u3059\u3002\u672c\u8a18\u4e8b\u3067\u306fTypeScript\u306e5\u3064\u306e\u30e1\u30ea\u30c3\u30c8\u3092\u5177\u4f53\u7684\u306a\u30b3\u30fc\u30c9\u4f8b\u3068\u3068\u3082\u306b\u89e3\u8aac\u3057\u3001React\u30fbNext.js\u30fbVue 3\u3067\u306e\u6d3b\u7528\u6cd5\u3082\u7d39\u4ecb\u3057\u307e\u3059\u3002<\/p>\n\n\n\n

    \n\n\n\n

    TypeScript\u3068\u306f\u4f55\u304b\uff5c\u578b\u5b89\u5168\u6027\u306e\u57fa\u672c<\/h2>\n\n\n\n

    TypeScript\u306fMicrosoft\u304c\u958b\u767a\u3057\u305fJavaScript\u306b\u578b\u30b7\u30b9\u30c6\u30e0\u3092\u8ffd\u52a0\u3057\u305f\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u8a00\u8a9e<\/strong>\u3067\u3059\u3002JavaScript\u306e\u30b9\u30fc\u30d1\u30fc\u30bb\u30c3\u30c8\uff08\u4e0a\u4f4d\u4e92\u63db\uff09\u3068\u3057\u3066\u8a2d\u8a08\u3055\u308c\u3066\u304a\u308a\u3001\u65e2\u5b58\u306eJavaScript\u30b3\u30fc\u30c9\u306f\u305d\u306e\u307e\u307eTypeScript\u3068\u3057\u3066\u52d5\u4f5c\u3057\u307e\u3059\u3002<\/p>\n\n\n\n \n
    \u7279\u5fb4<\/th>\u5185\u5bb9<\/th><\/tr><\/thead>\n
    \u9759\u7684\u578b\u4ed8\u3051<\/strong><\/td>\u30b3\u30f3\u30d1\u30a4\u30eb\u6642\u306b\u578b\u30c1\u30a7\u30c3\u30af\u3092\u884c\u3044\u3001\u5b9f\u884c\u524d\u306b\u30d0\u30b0\u3092\u691c\u51fa<\/td><\/tr>\n
    JavaScript\u3078\u306e\u5909\u63db<\/strong><\/td>\u6700\u7d42\u7684\u306bJavaScript\u306b\u30c8\u30e9\u30f3\u30b9\u30d1\u30a4\u30eb\u3055\u308c\u3066\u30d6\u30e9\u30a6\u30b6\u3067\u52d5\u4f5c<\/td><\/tr>\n
    \u6700\u65b0\u306eECMAScript\u6a5f\u80fd<\/strong><\/td>ES2020\u4ee5\u964d\u306e\u6a5f\u80fd\u3092\u5148\u53d6\u308a\u3057\u3066\u4f7f\u3048\u308b<\/td><\/tr>\n
    \u5f37\u529b\u306a\u30a8\u30c7\u30a3\u30bf\u30b5\u30dd\u30fc\u30c8<\/strong><\/td>VSCode\u3068\u306e\u7d71\u5408\u304c\u512a\u308c\u3066\u304a\u308a\u88dc\u5b8c\u30fb\u30a8\u30e9\u30fc\u8868\u793a\u304c\u5145\u5b9f<\/td><\/tr>\n
    \u6bb5\u968e\u7684\u5c0e\u5165\u53ef\u80fd<\/strong><\/td>\u65e2\u5b58\u306eJavaScript\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\u306b\u5c11\u3057\u305a\u3064\u5c0e\u5165\u3067\u304d\u308b<\/td><\/tr>\n <\/tbody>\n<\/table>\n\n\n

    \u578b\u5b89\u5168\u6027\u304c\u306a\u3044\u3068\u4f55\u304c\u8d77\u304d\u308b\u304b<\/h3>\n\n\n\n
    \/\/ JavaScript\uff1a\u5b9f\u884c\u6642\u30a8\u30e9\u30fc\u304c\u767a\u751f\nfunction add(a, b) {\n  return a + b;\n}\n\n\/\/ \u6570\u5024\u3092\u671f\u5f85\u3057\u3066\u3044\u308b\u304c\u3001\u6587\u5b57\u5217\u3092\u6e21\u3057\u3066\u3057\u307e\u3046\nconst result = add(\"10\", 5); \/\/ \"105\"\uff08\u6587\u5b57\u5217\u9023\u7d50\uff09\nconsole.log(result * 2); \/\/ NaN\uff08\u610f\u56f3\u3057\u306a\u3044\u7d50\u679c\uff09\n\n\/\/ \u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306e\u30d7\u30ed\u30d1\u30c6\u30a3\u540d\u3092\u9593\u9055\u3048\u308b\nconst user = { name: \"\u592a\u90ce\", age: 25 };\nconsole.log(user.nama); \/\/ undefined\uff08typo\u306b\u6c17\u3065\u304b\u306a\u3044\uff09<\/code><\/pre>\n\n\n\n
    \/\/ TypeScript\uff1a\u30b3\u30f3\u30d1\u30a4\u30eb\u6642\u306b\u30a8\u30e9\u30fc\u3092\u691c\u51fa\nfunction add(a: number, b: number): number {\n  return a + b;\n}\n\n\/\/ \u274c \u30a8\u30e9\u30fc\uff1aArgument of type 'string' is not assignable to parameter of type 'number'\nconst result = add(\"10\", 5);\n\n\/\/ \u578b\u5b9a\u7fa9\u3067\u30d7\u30ed\u30d1\u30c6\u30a3\u3092\u660e\u793a\ninterface User {\n  name: string;\n  age: number;\n}\n\nconst user: User = { name: \"\u592a\u90ce\", age: 25 };\n\n\/\/ \u274c \u30a8\u30e9\u30fc\uff1aProperty 'nama' does not exist on type 'User'. Did you mean 'name'?\nconsole.log(user.nama);<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    TypeScript\u304cWeb\u5236\u4f5c\u306b\u3082\u305f\u3089\u30595\u3064\u306e\u30e1\u30ea\u30c3\u30c8<\/h2>\n\n\n\n
    \u30e1\u30ea\u30c3\u30c81\uff1a\u5b9f\u884c\u6642\u30a8\u30e9\u30fc\u306e\u5927\u5e45\u524a\u6e1b<\/h3>\n\n\n\n
    \u578b\u5b89\u5168\u6027\u306e\u6700\u5927\u306e\u30e1\u30ea\u30c3\u30c8\u306f\u5b9f\u884c\u524d\u306b\u30d0\u30b0\u3092\u767a\u898b\u3067\u304d\u308b<\/strong>\u3053\u3068\u3067\u3059\u3002JavaScript\u3067\u306f\u5b9f\u884c\u6642\u306b\u3057\u304b\u767a\u898b\u3067\u304d\u306a\u304b\u3063\u305f\u30a8\u30e9\u30fc\u3092\u3001\u30b3\u30fc\u30c9\u3092\u66f8\u3044\u3066\u3044\u308b\u6bb5\u968e\u3067\u9632\u3052\u307e\u3059\u3002<\/p>\n\n\n\n
    \/\/ JavaScript\uff1a\u5b9f\u884c\u6642\u306b\u30a8\u30e9\u30fc\nfunction getUserName(user) {\n  return user.profile.name; \/\/ user\u304cnull\u3084undefined\u3060\u3068\u30a8\u30e9\u30fc\n}\n\nconst result = getUserName(null);\n\/\/ \u274c Uncaught TypeError: Cannot read properties of null (reading 'profile')<\/code><\/pre>\n\n\n\n
    \/\/ TypeScript\uff1a\u578b\u3067null\u3092\u660e\u793a\u7684\u306b\u6271\u3046\ninterface Profile {\n  name: string;\n}\n\ninterface User {\n  profile: Profile;\n}\n\nfunction getUserName(user: User | null): string {\n  \/\/ \u274c \u30a8\u30e9\u30fc\uff1aObject is possibly 'null'\n  \/\/ return user.profile.name;\n\n  \/\/ \u2705 \u6b63\u3057\u3044\u5b9f\u88c5\uff1anull\u30c1\u30a7\u30c3\u30af\u3092\u5f37\u5236\u3055\u308c\u308b\n  if (user === null) {\n    return \"\u30b2\u30b9\u30c8\";\n  }\n  return user.profile.name;\n}\n\nconst result = getUserName(null); \/\/ \"\u30b2\u30b9\u30c8\"<\/code><\/pre>\n\n\n\n
    \/\/ \u3088\u308a\u7c21\u6f54\u306a\u66f8\u304d\u65b9\nfunction getUserName(user: User | null): string {\n  return user?.profile?.name ?? \"\u30b2\u30b9\u30c8\";\n}\n\n\/\/ \u914d\u5217\u306e\u5b89\u5168\u306a\u64cd\u4f5c\nfunction getFirstUserName(users: User[]): string {\n  return users[0]?.profile?.name ?? \"\u30e6\u30fc\u30b6\u30fc\u306a\u3057\";\n}<\/code><\/pre>\n\n\n\n
    \u30e1\u30ea\u30c3\u30c82\uff1a\u5f37\u529b\u306a\u30a8\u30c7\u30a3\u30bf\u30b5\u30dd\u30fc\u30c8\u3068\u30b3\u30fc\u30c9\u88dc\u5b8c<\/h3>\n\n\n\n
    TypeScript\u3092\u4f7f\u3046\u3068VSCode\u306a\u3069\u306e\u30a8\u30c7\u30a3\u30bf\u304c\u5287\u7684\u306b\u8ce2\u304f<\/strong>\u306a\u308a\u307e\u3059\u3002\u578b\u60c5\u5831\u3092\u3082\u3068\u306b\u3001\u6b63\u78ba\u306a\u30b3\u30fc\u30c9\u88dc\u5b8c\u30fb\u30ea\u30d5\u30a1\u30af\u30bf\u30ea\u30f3\u30b0\u30fb\u30ca\u30d3\u30b2\u30fc\u30b7\u30e7\u30f3\u652f\u63f4\u3092\u63d0\u4f9b\u3057\u3066\u304f\u308c\u307e\u3059\u3002<\/p>\n\n\n\n
    interface Product {\n  id: number;\n  name: string;\n  price: number;\n  category: \"electronics\" | \"books\" | \"clothing\";\n  inStock: boolean;\n}\n\nconst product: Product = {\n  id: 1,\n  name: \"\u30ce\u30fc\u30c8PC\",\n  price: 120000,\n  category: \"electronics\",\n  inStock: true,\n};\n\n\/\/ \"product.\" \u3068\u5165\u529b\u3059\u308b\u3068\u3001\u30a8\u30c7\u30a3\u30bf\u304c\u81ea\u52d5\u7684\u306b\u4ee5\u4e0b\u3092\u63d0\u6848\n\/\/ - id\n\/\/ - name\n\/\/ - price\n\/\/ - category\n\/\/ - inStock\n\n\/\/ \u274c \u5b58\u5728\u3057\u306a\u3044\u30d7\u30ed\u30d1\u30c6\u30a3\u306b\u30a2\u30af\u30bb\u30b9\u3057\u3088\u3046\u3068\u3059\u308b\u3068\u30a8\u30e9\u30fc\nconsole.log(product.description); \/\/ Property 'description' does not exist<\/code><\/pre>\n\n\n\n
    \/\/ \u95a2\u6570\u306e\u5f15\u6570\u306b\u30ab\u30fc\u30bd\u30eb\u3092\u5408\u308f\u305b\u308b\u3068\u3001\u578b\u60c5\u5831\u304c\u8868\u793a\u3055\u308c\u308b\nfunction filterProducts(\n  products: Product[],\n  category: Product[\"category\"]\n): Product[] {\n  return products.filter((p) => p.category === category);\n}\n\n\/\/ \u95a2\u6570\u3092\u547c\u3073\u51fa\u3059\u3068\u304d\u3001\u5f15\u6570\u306e\u578b\u304c\u8868\u793a\u3055\u308c\u308b\n\/\/ filterProducts(products, ???)\n\/\/                         \u2191 \u3053\u3053\u3067 \"electronics\" | \"books\" | \"clothing\" \u3068\u8868\u793a\n\nconst electronics = filterProducts(products, \"electronics\");\n\n\/\/ \u274c \u5b58\u5728\u3057\u306a\u3044\u30ab\u30c6\u30b4\u30ea\u30fc\u3092\u6307\u5b9a\u3059\u308b\u3068\u30a8\u30e9\u30fc\nconst toys = filterProducts(products, \"toys\");<\/code><\/pre>\n\n\n\n
    \u30d7\u30ed\u30d1\u30c6\u30a3\u540d\u3084\u30e1\u30bd\u30c3\u30c9\u540d\u3092\u5909\u66f4\u3059\u308b\u3068\u3001\u3059\u3079\u3066\u306e\u4f7f\u7528\u7b87\u6240\u3092\u81ea\u52d5\u7684\u306b\u66f4\u65b0<\/strong>\u3059\u308b\u30ea\u30cd\u30fc\u30e0\u6a5f\u80fd\uff08Rename Symbol\uff09\u3082 TypeScript \u74b0\u5883\u3067\u3053\u305d\u78ba\u5b9f\u306b\u6a5f\u80fd\u3057\u307e\u3059\u3002<\/p>\n\n\n\n
    \u30e1\u30ea\u30c3\u30c83\uff1a\u30c1\u30fc\u30e0\u958b\u767a\u3067\u306e\u6a19\u6e96\u5316\u3068\u53ef\u8aad\u6027\u5411\u4e0a<\/h3>\n\n\n\n
    TypeScript\u306e\u578b\u5b9a\u7fa9\u306f\u30b3\u30fc\u30c9\u306e\u30c9\u30ad\u30e5\u30e1\u30f3\u30c8\u3068\u3057\u3066\u3082\u6a5f\u80fd<\/strong>\u3057\u307e\u3059\u3002\u30c1\u30fc\u30e0\u30e1\u30f3\u30d0\u30fc\u5168\u54e1\u304c\u540c\u3058\u7406\u89e3\u306e\u3082\u3068\u3067\u30b3\u30fc\u30c9\u3092\u66f8\u3051\u308b\u305f\u3081\u3001\u30ec\u30d3\u30e5\u30fc\u3084\u5f15\u304d\u7d99\u304e\u304c\u30b9\u30e0\u30fc\u30ba\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n\n\n\n
    \/\/ \u274c JavaScript\uff1a\u95a2\u6570\u306e\u4ed5\u69d8\u304c\u4e0d\u660e\u78ba\nfunction createOrder(userId, items, shippingAddress) {\n  \/\/ items\u306f\u914d\u5217\uff1f\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\uff1f\n  \/\/ shippingAddress\u306f\u3069\u3093\u306a\u5f62\u5f0f\uff1f\n  \/\/ \u623b\u308a\u5024\u306f\u4f55\uff1f\n}\n\n\/\/ \u2705 TypeScript\uff1a\u578b\u5b9a\u7fa9\u3067\u4ed5\u69d8\u304c\u660e\u78ba\ninterface OrderItem {\n  productId: number;\n  quantity: number;\n  price: number;\n}\n\ninterface ShippingAddress {\n  postalCode: string;\n  prefecture: string;\n  city: string;\n  addressLine1: string;\n  addressLine2?: string; \/\/ \u30aa\u30d7\u30b7\u30e7\u30ca\u30eb\n}\n\ninterface Order {\n  orderId: string;\n  userId: number;\n  items: OrderItem[];\n  totalAmount: number;\n  shippingAddress: ShippingAddress;\n  createdAt: Date;\n}\n\nfunction createOrder(\n  userId: number,\n  items: OrderItem[],\n  shippingAddress: ShippingAddress\n): Promise {\n  \/\/ \u5b9f\u88c5\n  \/\/ \u578b\u5b9a\u7fa9\u3092\u898b\u308b\u3060\u3051\u3067\u3001\u5f15\u6570\u3068\u623b\u308a\u5024\u306e\u5f62\u5f0f\u304c\u308f\u304b\u308b\n}<\/code><\/pre>\n\n\n\n
    \/\/ \u30d0\u30c3\u30af\u30a8\u30f3\u30c9\u3068\u30d5\u30ed\u30f3\u30c8\u30a8\u30f3\u30c9\u3067\u578b\u5b9a\u7fa9\u3092\u5171\u6709\n\/\/ types\/api.ts\nexport interface GetUsersResponse {\n  users: User[];\n  totalCount: number;\n  page: number;\n  perPage: number;\n}\n\nexport interface CreateUserRequest {\n  name: string;\n  email: string;\n  password: string;\n}\n\nexport interface CreateUserResponse {\n  user: User;\n  token: string;\n}\n\n\/\/ \u30d5\u30ed\u30f3\u30c8\u30a8\u30f3\u30c9\uff1a\u578b\u5b89\u5168\u306aAPI\u547c\u3073\u51fa\u3057\nasync function fetchUsers(): Promise {\n  const response = await fetch(\"\/api\/users\");\n  const data: GetUsersResponse = await response.json();\n  return data;\n}\n\n\/\/ \u30d0\u30c3\u30af\u30a8\u30f3\u30c9\uff08Node.js + Express\uff09\uff1a\u540c\u3058\u578b\u5b9a\u7fa9\u3092\u4f7f\u7528\napp.get(\"\/api\/users\", async (req, res) => {\n  const response: GetUsersResponse = {\n    users: await db.getUsers(),\n    totalCount: await db.getUserCount(),\n    page: 1,\n    perPage: 20,\n  };\n  res.json(response);\n});<\/code><\/pre>\n\n\n\n
    \u30e1\u30ea\u30c3\u30c84\uff1a\u30ea\u30d5\u30a1\u30af\u30bf\u30ea\u30f3\u30b0\u306e\u5b89\u5168\u6027<\/h3>\n\n\n\n
    \u5927\u898f\u6a21\u306a\u30b3\u30fc\u30c9\u5909\u66f4\u3084\u6a5f\u80fd\u8ffd\u52a0\u3092\u884c\u3046\u969b\u3001TypeScript\u306e\u578b\u30c1\u30a7\u30c3\u30af\u304c\u5f71\u97ff\u7bc4\u56f2\u3092\u6b63\u78ba\u306b\u628a\u63e1<\/strong>\u3059\u308b\u624b\u52a9\u3051\u3092\u3057\u3066\u304f\u308c\u307e\u3059\u3002<\/p>\n\n\n\n
    \/\/ Before\uff1a\u65e2\u5b58\u306e\u30a4\u30f3\u30bf\u30fc\u30d5\u30a7\u30fc\u30b9\ninterface User {\n  id: number;\n  name: string;\n  email: string;\n}\n\n\/\/ After\uff1a\u65b0\u3057\u3044\u30d7\u30ed\u30d1\u30c6\u30a3\u3092\u8ffd\u52a0\ninterface User {\n  id: number;\n  name: string;\n  email: string;\n  avatar?: string; \/\/ \u65b0\u898f\u8ffd\u52a0\uff08\u30aa\u30d7\u30b7\u30e7\u30ca\u30eb\uff09\n  role: \"admin\" | \"user\"; \/\/ \u65b0\u898f\u8ffd\u52a0\uff08\u5fc5\u9808\uff09\n}\n\n\/\/ \u274c \u578b\u30a8\u30e9\u30fc\u3067\u5f71\u97ff\u7bc4\u56f2\u304c\u3059\u3050\u306b\u308f\u304b\u308b\nconst users: User[] = [\n  { id: 1, name: \"\u592a\u90ce\", email: \"taro@example.com\" }, \/\/ \u30a8\u30e9\u30fc\uff1arole\u304c\u306a\u3044\n  { id: 2, name: \"\u82b1\u5b50\", email: \"hanako@example.com\" }, \/\/ \u30a8\u30e9\u30fc\uff1arole\u304c\u306a\u3044\n];\n\n\/\/ \u2705 \u4fee\u6b63\nconst users: User[] = [\n  { id: 1, name: \"\u592a\u90ce\", email: \"taro@example.com\", role: \"user\" },\n  { id: 2, name: \"\u82b1\u5b50\", email: \"hanako@example.com\", role: \"admin\" },\n];<\/code><\/pre>\n\n\n\n
    \/\/ \u53e4\u3044API\u3068\u65b0\u3057\u3044API\u304c\u6df7\u5728\u3059\u308b\u671f\u9593\u306e\u578b\u5b9a\u7fa9\ntype LegacyUser = {\n  user_id: number; \/\/ snake_case\n  user_name: string;\n};\n\ntype ModernUser = {\n  id: number; \/\/ camelCase\n  name: string;\n  email: string;\n};\n\n\/\/ \u4e21\u65b9\u306e\u5f62\u5f0f\u3092\u53d7\u3051\u5165\u308c\u308b\ntype User = LegacyUser | ModernUser;\n\nfunction displayUser(user: User) {\n  \/\/ \u578b\u30ac\u30fc\u30c9\u3067\u5206\u5c90\n  if (\"user_id\" in user) {\n    \/\/ LegacyUser\n    console.log(`ID: ${user.user_id}, Name: ${user.user_name}`);\n  } else {\n    \/\/ ModernUser\n    console.log(`ID: ${user.id}, Name: ${user.name}`);\n  }\n}<\/code><\/pre>\n\n\n\n
    \u30e1\u30ea\u30c3\u30c85\uff1a\u6700\u65b0\u306eJavaScript\u6a5f\u80fd\u3092\u5148\u53d6\u308a<\/h3>\n\n\n\n
    TypeScript\u306f\u6700\u65b0\u306eECMAScript\u6a5f\u80fd\u3092\u65e9\u671f\u306b\u30b5\u30dd\u30fc\u30c8<\/strong>\u3057\u3001\u53e4\u3044\u30d6\u30e9\u30a6\u30b6\u5411\u3051\u306e\u30b3\u30fc\u30c9\u306b\u30c8\u30e9\u30f3\u30b9\u30d1\u30a4\u30eb\u3057\u3066\u304f\u308c\u307e\u3059\u3002<\/p>\n\n\n\n
    \/\/ Optional Chaining\uff08ES2020\uff09\nconst userName = user?.profile?.name;\n\n\/\/ Nullish Coalescing\uff08ES2020\uff09\nconst displayName = user?.name ?? \"\u30b2\u30b9\u30c8\";\n\n\/\/ Private Fields\uff08ES2022\uff09\nclass BankAccount {\n  #balance: number = 0; \/\/ \u30d7\u30e9\u30a4\u30d9\u30fc\u30c8\u30d5\u30a3\u30fc\u30eb\u30c9\n\n  deposit(amount: number) {\n    this.#balance += amount;\n  }\n\n  getBalance(): number {\n    return this.#balance;\n  }\n}\n\n\/\/ Top-level await\uff08ES2022\uff09\nconst data = await fetch(\"\/api\/data\").then(r => r.json());\n\n\/\/ tsconfig.json\u3067\u53e4\u3044\u30d6\u30e9\u30a6\u30b6\u5411\u3051\u306b\u5909\u63db\n\/\/ \"target\": \"ES5\" \u2192 IE11\u3067\u3082\u52d5\u4f5c\u3059\u308b\u30b3\u30fc\u30c9\u306b\u5909\u63db\u3055\u308c\u308b<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    TypeScript\u306e\u5c0e\u5165\u65b9\u6cd5<\/h2>\n\n\n\n
    \u65b0\u898f\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\u3067\u306e\u5c0e\u5165<\/h3>\n\n\n\n
    # npm\nnpm install --save-dev typescript\n\n# yarn\nyarn add --dev typescript\n\n# pnpm\npnpm add -D typescript\n\n# TypeScript\u30d0\u30fc\u30b8\u30e7\u30f3\u78ba\u8a8d\nnpx tsc --version<\/code><\/pre>\n\n\n\n
    # \u521d\u671f\u5316\u30b3\u30de\u30f3\u30c9\nnpx tsc --init\n\n# \u751f\u6210\u3055\u308c\u308btsconfig.json\uff08\u63a8\u5968\u8a2d\u5b9a\uff09\n{\n  \"compilerOptions\": {\n    \"target\": \"ES2020\",                    \/\/ \u51fa\u529b\u3059\u308bJavaScript\u306e\u30d0\u30fc\u30b8\u30e7\u30f3\n    \"module\": \"ESNext\",                    \/\/ \u30e2\u30b8\u30e5\u30fc\u30eb\u30b7\u30b9\u30c6\u30e0\n    \"lib\": [\"ES2020\", \"DOM\"],              \/\/ \u4f7f\u7528\u3059\u308b\u30e9\u30a4\u30d6\u30e9\u30ea\n    \"jsx\": \"react-jsx\",                    \/\/ React\u4f7f\u7528\u6642\n    \"strict\": true,                        \/\/ \u53b3\u683c\u306a\u578b\u30c1\u30a7\u30c3\u30af\n    \"esModuleInterop\": true,               \/\/ CommonJS\u3068\u306e\u4e92\u63db\u6027\n    \"skipLibCheck\": true,                  \/\/ \u30e9\u30a4\u30d6\u30e9\u30ea\u306e\u578b\u30c1\u30a7\u30c3\u30af\u3092\u30b9\u30ad\u30c3\u30d7\n    \"forceConsistentCasingInFileNames\": true,\n    \"moduleResolution\": \"node\",\n    \"resolveJsonModule\": true,\n    \"isolatedModules\": true,\n    \"noEmit\": true,                        \/\/ Vite\u306a\u3069\u4ed6\u306e\u30c4\u30fc\u30eb\u3067\u30d3\u30eb\u30c9\u3059\u308b\u5834\u5408\n    \"outDir\": \".\/dist\",                    \/\/ \u51fa\u529b\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\n    \"rootDir\": \".\/src\",                    \/\/ \u30bd\u30fc\u30b9\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\n  },\n  \"include\": [\"src\/**\/*\"],\n  \"exclude\": [\"node_modules\", \"dist\"]\n}<\/code><\/pre>\n\n\n\n
    \/\/ src\/index.ts\nfunction greet(name: string): string {\n  return `Hello, ${name}!`;\n}\n\nconst message = greet(\"TypeScript\");\nconsole.log(message);\n\n\/\/ \u30b3\u30f3\u30d1\u30a4\u30eb\u5b9f\u884c\nnpx tsc\n\n\/\/ \u751f\u6210\u3055\u308c\u305fJavaScript\u30d5\u30a1\u30a4\u30eb\uff08dist\/index.js\uff09\u3092\u5b9f\u884c\nnode dist\/index.js<\/code><\/pre>\n\n\n\n
    \u65e2\u5b58\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\u3078\u306e\u6bb5\u968e\u7684\u5c0e\u5165<\/h3>\n\n\n\n
    # TypeScript\u306e\u30a4\u30f3\u30b9\u30c8\u30fc\u30eb\nnpm install --save-dev typescript @types\/node\n\n# tsconfig.json\u4f5c\u6210\uff08\u7de9\u3044\u8a2d\u5b9a\u304b\u3089\u958b\u59cb\uff09\n{\n  \"compilerOptions\": {\n    \"allowJs\": true,              \/\/ JavaScript\u30d5\u30a1\u30a4\u30eb\u3082\u542b\u3081\u308b\n    \"checkJs\": false,             \/\/ JavaScript\u30d5\u30a1\u30a4\u30eb\u306f\u578b\u30c1\u30a7\u30c3\u30af\u3057\u306a\u3044\n    \"strict\": false,              \/\/ \u6700\u521d\u306f\u7de9\u3044\u8a2d\u5b9a\n    \"noImplicitAny\": false,\n    \"target\": \"ES2020\",\n    \"module\": \"ESNext\",\n    \"moduleResolution\": \"node\",\n    \"esModuleInterop\": true\n  },\n  \"include\": [\"src\/**\/*\"]\n}<\/code><\/pre>\n\n\n\n
    \/\/ Before: utils.js\nexport function formatPrice(price) {\n  return `\u00a5${price.toLocaleString()}`;\n}\n\n\/\/ After: utils.ts\uff08\u578b\u3092\u8ffd\u52a0\uff09\nexport function formatPrice(price: number): string {\n  return `\u00a5${price.toLocaleString()}`;\n}<\/code><\/pre>\n\n\n\n
    \/\/ tsconfig.json\u3092\u6bb5\u968e\u7684\u306b\u53b3\u683c\u5316\n{\n  \"compilerOptions\": {\n    \/\/ \u30d5\u30a7\u30fc\u30ba1\uff1a\u57fa\u672c\u7684\u306a\u578b\u30c1\u30a7\u30c3\u30af\n    \"noImplicitAny\": true,        \/\/ any\u578b\u3092\u660e\u793a\u7684\u306b\u66f8\u304f\u3053\u3068\u3092\u5f37\u5236\n\n    \/\/ \u30d5\u30a7\u30fc\u30ba2\uff1anull\/undefined\u306e\u30c1\u30a7\u30c3\u30af\n    \"strictNullChecks\": true,     \/\/ null\/undefined\u3092\u53b3\u683c\u306b\u30c1\u30a7\u30c3\u30af\n\n    \/\/ \u30d5\u30a7\u30fc\u30ba3\uff1a\u305d\u306e\u4ed6\u306e\u53b3\u683c\u8a2d\u5b9a\n    \"strictFunctionTypes\": true,\n    \"strictBindCallApply\": true,\n    \"strictPropertyInitialization\": true,\n\n    \/\/ \u30d5\u30a7\u30fc\u30ba4\uff1a\u3059\u3079\u3066\u6709\u52b9\u5316\n    \"strict\": true\n  }\n}<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    \u30d5\u30ec\u30fc\u30e0\u30ef\u30fc\u30af\u5225TypeScript\u6d3b\u7528\u6cd5<\/h2>\n\n\n\n
    React + TypeScript<\/h3>\n\n\n\n
    # Vite + React + TypeScript\nnpm create vite@latest my-app -- --template react-ts\n\n# Next.js + TypeScript\uff08\u81ea\u52d5\u7684\u306bTypeScript\u8a2d\u5b9a\uff09\nnpx create-next-app@latest my-app --typescript<\/code><\/pre>\n\n\n\n
    \/\/ Props\u578b\u306e\u5b9a\u7fa9\ninterface ButtonProps {\n  label: string;\n  onClick: () => void;\n  variant?: \"primary\" | \"secondary\" | \"danger\";\n  disabled?: boolean;\n}\n\n\/\/ \u95a2\u6570\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\nexport function Button({ label, onClick, variant = \"primary\", disabled = false }: ButtonProps) {\n  return (\n    <button\n      onClick={onClick}\n      disabled={disabled}\n      className={`btn btn-${variant}`}\n    >\n      {label}\n    <\/button>\n  );\n}\n\n\/\/ React.FC\u3092\u4f7f\u3063\u305f\u66f8\u304d\u65b9\nexport const Button: React.FC = ({ label, onClick, variant = \"primary\", disabled = false }) => {\n  return (\n    <button onClick={onClick} disabled={disabled} className={`btn btn-${variant}`}>\n      {label}\n    <\/button>\n  );\n};<\/code><\/pre>\n\n\n\n
    import { useState, useEffect } from \"react\";\n\ninterface User {\n  id: number;\n  name: string;\n  email: string;\n}\n\nexport function UserProfile({ userId }: { userId: number }) {\n  \/\/ useState\uff1a\u578b\u63a8\u8ad6\u304c\u52b9\u304f\n  const [user, setUser] = useState(null);\n  const [loading, setLoading] = useState(true);\n  const [error, setError] = useState(null);\n\n  useEffect(() => {\n    async function fetchUser() {\n      try {\n        setLoading(true);\n        const response = await fetch(`\/api\/users\/${userId}`);\n        const data: User = await response.json();\n        setUser(data);\n      } catch (err) {\n        setError(err instanceof Error ? err.message : \"Unknown error\");\n      } finally {\n        setLoading(false);\n      }\n    }\n\n    fetchUser();\n  }, [userId]);\n\n  if (loading) return <div>\u8aad\u307f\u8fbc\u307f\u4e2d...<\/div>;\n  if (error) return <div>\u30a8\u30e9\u30fc: {error}<\/div>;\n  if (!user) return <div>\u30e6\u30fc\u30b6\u30fc\u304c\u898b\u3064\u304b\u308a\u307e\u305b\u3093<\/div>;\n\n  return (\n    <div>\n      <h2>{user.name}<\/h2>\n      <p>{user.email}<\/p>\n    <\/div>\n  );\n}<\/code><\/pre>\n\n\n\n
    Next.js + TypeScript<\/h3>\n\n\n\n
    import type { GetServerSideProps, NextPage } from \"next\";\n\ninterface PageProps {\n  user: User;\n}\n\n\/\/ \u30da\u30fc\u30b8\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\nconst UserPage: NextPage = ({ user }) => {\n  return (\n    <div>\n      <h1>{user.name}<\/h1>\n      <p>{user.email}<\/p>\n    <\/div>\n  );\n};\n\n\/\/ getServerSideProps\u306e\u578b\u5b9a\u7fa9\nexport const getServerSideProps: GetServerSideProps = async (context) => {\n  const { id } = context.params!;\n  const response = await fetch(`https:\/\/api.example.com\/users\/${id}`);\n  const user: User = await response.json();\n\n  return {\n    props: { user },\n  };\n};\n\nexport default UserPage;<\/code><\/pre>\n\n\n\n
    import type { NextApiRequest, NextApiResponse } from \"next\";\n\ninterface User {\n  id: number;\n  name: string;\n  email: string;\n}\n\ntype ErrorResponse = {\n  error: string;\n};\n\n\/\/ API Route\u30cf\u30f3\u30c9\u30e9\u30fc\nexport default async function handler(\n  req: NextApiRequest,\n  res: NextApiResponse\n) {\n  if (req.method !== \"GET\") {\n    return res.status(405).json({ error: \"Method not allowed\" });\n  }\n\n  try {\n    const { id } = req.query;\n    const user = await db.getUser(Number(id));\n\n    if (!user) {\n      return res.status(404).json({ error: \"User not found\" });\n    }\n\n    res.status(200).json(user);\n  } catch (error) {\n    res.status(500).json({ error: \"Internal server error\" });\n  }\n}<\/code><\/pre>\n\n\n\n
    Vue 3 + TypeScript<\/h3>\n\n\n\n
    Vue 3\u3067\u306fComposition API\u3068TypeScript\u306e\u89aa\u548c\u6027\u304c\u5927\u5e45\u306b\u5411\u4e0a\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n\n\n\n
    # Vite + Vue 3 + TypeScript\nnpm create vite@latest my-app -- --template vue-ts<\/code><\/pre>\n\n\n\n
    <script setup lang=\"ts\">\nimport { ref, computed, onMounted } from \"vue\";\n\ninterface User {\n  id: number;\n  name: string;\n  email: string;\n}\n\ninterface Props {\n  userId: number;\n}\n\n\/\/ Props\u578b\u306e\u5b9a\u7fa9\nconst props = defineProps();\n\n\/\/ Emit\u30a4\u30d9\u30f3\u30c8\u306e\u578b\u5b9a\u7fa9\nconst emit = defineEmits<{\n  userLoaded: [user: User];\n  error: [message: string];\n}>();\n\n\/\/ ref\uff1a\u578b\u63a8\u8ad6\u304c\u52b9\u304f\nconst user = ref(null);\nconst loading = ref(true);\n\n\/\/ computed\uff1a\u623b\u308a\u5024\u306e\u578b\u304c\u81ea\u52d5\u63a8\u8ad6\u3055\u308c\u308b\nconst displayName = computed(() => {\n  return user.value ? user.value.name : \"\u30b2\u30b9\u30c8\";\n});\n\n\/\/ \u95a2\u6570\u306e\u578b\u5b9a\u7fa9\nasync function fetchUser(): Promise {\n  try {\n    loading.value = true;\n    const response = await fetch(`\/api\/users\/${props.userId}`);\n    const data: User = await response.json();\n    user.value = data;\n    emit(\"userLoaded\", data);\n  } catch (err) {\n    const message = err instanceof Error ? err.message : \"Unknown error\";\n    emit(\"error\", message);\n  } finally {\n    loading.value = false;\n  }\n}\n\nonMounted(() => {\n  fetchUser();\n});\n<\/script>\n\n<template>\n  <div v-if=\"loading\">\u8aad\u307f\u8fbc\u307f\u4e2d...<\/div>\n  <div v-else-if=\"user\">\n    <h2>{{ displayName }}<\/h2>\n    <p>{{ user.email }}<\/p>\n  <\/div>\n<\/template><\/code><\/pre>\n\n\n\n
    \n\n\n\n
    TypeScript\u306e\u30c7\u30e1\u30ea\u30c3\u30c8\u3068\u5bfe\u51e6\u6cd5<\/h2>\n\n\n\n  \n    
    \u30c7\u30e1\u30ea\u30c3\u30c8<\/th>\u5bfe\u51e6\u6cd5<\/th><\/tr><\/thead>\n  
    \u5b66\u7fd2\u30b3\u30b9\u30c8<\/strong>\uff1a\u30b8\u30a7\u30cd\u30ea\u30af\u30b9\u30fbUnion\u578b\u30fbUtility Types\u306e\u7fd2\u5f97\u306b\u6642\u9593\u304c\u304b\u304b\u308b<\/td>\u57fa\u672c\u7684\u306a\u578b\uff08string\u30fbnumber\u30fbboolean\uff09\u304b\u3089\u59cb\u3081\u3001\u516c\u5f0fTypeScript Handbook\u3067\u6bb5\u968e\u7684\u306b\u5b66\u3076<\/td><\/tr>\n    
    \u521d\u671f\u8a2d\u5b9a\u306e\u624b\u9593<\/strong>\uff1atsconfig.json\u3084\u578b\u5b9a\u7fa9\u30d5\u30a1\u30a4\u30eb\u306e\u8a2d\u5b9a\u304c\u5fc5\u8981<\/td>Vite\u30fbNext.js\u306a\u3069\u306e\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u3092\u4f7f\u3046\u3002@tsconfig\/recommended\u3067\u5171\u6709\u8a2d\u5b9a\u3092\u6d3b\u7528<\/td><\/tr>\n    
    \u5c0f\u898f\u6a21\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\u306e\u30aa\u30fc\u30d0\u30fc\u30d8\u30c3\u30c9<\/strong>\uff1a\u578b\u5b9a\u7fa9\u306e\u624b\u9593\u304c\u52b9\u679c\u3092\u4e0a\u56de\u308b\u3053\u3068\u304c\u3042\u308b<\/td>\u5358\u767a\u30c4\u30fc\u30eb\u30fb\u77ed\u671f\u691c\u8a3c\u306fJavaScript\u3001\u30c1\u30fc\u30e0\u958b\u767a\u30fb\u9577\u671f\u904b\u7528\u306fTypeScript\u3068\u4f7f\u3044\u5206\u3051\u308b<\/td><\/tr>\n  <\/tbody>\n<\/table>\n\n\n
    \n\n\n\n
    TypeScript\u5c0e\u5165\u306e\u5224\u65ad\u57fa\u6e96<\/h2>\n\n\n\n  \n    
    TypeScript\u3092\u63a8\u5968\u3059\u308b\u30b1\u30fc\u30b9<\/th>JavaScript\u3067\u5341\u5206\u306a\u30b1\u30fc\u30b9<\/th><\/tr><\/thead>\n  
    \u30c1\u30fc\u30e0\u958b\u767a\uff082\u4eba\u4ee5\u4e0a\uff09<\/td>\u5358\u767a\u30c4\u30fc\u30eb\u30fb\u4f7f\u3044\u6368\u3066\u30b9\u30af\u30ea\u30d7\u30c8<\/td><\/tr>\n    
    \u9577\u671f\u904b\u7528\uff08\u534a\u5e74\u4ee5\u4e0a\uff09<\/td>\u77ed\u671f\u691c\u8a3c\uff081\u301c2\u9031\u9593\u306e PoC\uff09<\/td><\/tr>\n    
    \u7d99\u7d9a\u7684\u306a\u6a5f\u80fd\u8ffd\u52a0\uff08\u30a2\u30b8\u30e3\u30a4\u30eb\u958b\u767a\uff09<\/td>100\u884c\u672a\u6e80\u306e\u30b7\u30f3\u30d7\u30eb\u306a\u30b9\u30af\u30ea\u30d7\u30c8<\/td><\/tr>\n    
    \u8907\u96d1\u306a\u30d3\u30b8\u30cd\u30b9\u30ed\u30b8\u30c3\u30af<\/td>JavaScript\u81ea\u4f53\u3092\u5b66\u3093\u3067\u3044\u308b\u521d\u5fc3\u8005<\/td><\/tr>\n    
    \u5916\u90e8API\u9023\u643a\u304c\u591a\u3044<\/td>\u65e2\u5b58\u8cc7\u7523\u304c\u5927\u91cf\u3067\u79fb\u884c\u30b3\u30b9\u30c8\u304c\u9ad8\u3044<\/td><\/tr>\n  <\/tbody>\n<\/table>\n\n\n
    \n\n\n\n
    \u3088\u304f\u3042\u308b\u8cea\u554f\uff08FAQ\uff09<\/h2>\n\n\n\n
    TypeScript\u3092\u5b66\u3076\u524d\u306bJavaScript\u3092\u30de\u30b9\u30bf\u30fc\u3059\u3079\u304d\u3067\u3059\u304b\uff1f<\/h3>\n\n\n\n
    JavaScript\u306e\u57fa\u790e\uff08\u5909\u6570\u30fb\u95a2\u6570\u30fb\u975e\u540c\u671f\u51e6\u7406\u30fbDOM\u64cd\u4f5c\uff09\u3092\u7406\u89e3\u3057\u3066\u304b\u3089TypeScript\u306b\u9032\u3080\u306e\u304c\u6700\u77ed\u30eb\u30fc\u30c8\u3067\u3059\u3002TypeScript\u306fJavaScript\u306e\u4e0a\u4f4d\u4e92\u63db\u306a\u306e\u3067\u3001JavaScript\u3092\u66f8\u3051\u306a\u3044\u72b6\u614b\u3067TypeScript\u306e\u578b\u30b7\u30b9\u30c6\u30e0\u3060\u3051\u3092\u5b66\u3093\u3067\u3082\u6df7\u4e71\u3057\u307e\u3059\u3002\u76ee\u5b89\u3068\u3057\u3066\u3001JavaScript\u3067\u7c21\u5358\u306aWeb\u30a2\u30d7\u30ea\u3092\u4f5c\u308c\u308b\u30ec\u30d9\u30eb\u306b\u306a\u3063\u3066\u304b\u3089\u79fb\u884c\u3057\u307e\u3057\u3087\u3046\u3002<\/p>\n\n\n\n
    any\u578b\u3092\u4f7f\u3046\u306e\u306f\u306a\u305c\u907f\u3051\u308b\u3079\u304d\u3067\u3059\u304b\uff1f<\/h3>\n\n\n\n
    any<\/code>\u578b\u3092\u4f7f\u3046\u3068\u305d\u306e\u5909\u6570\u306e\u578b\u30c1\u30a7\u30c3\u30af\u304c\u5b8c\u5168\u306b\u7121\u52b9\u5316\u3055\u308c\u3001TypeScript\u3092\u4f7f\u3046\u610f\u5473\u304c\u306a\u304f\u306a\u308a\u307e\u3059\u3002\u3069\u3046\u3057\u3066\u3082\u578b\u304c\u4e0d\u660e\u306a\u5834\u5408\u306funknown<\/code>\u578b\u3092\u4f7f\u3044\u3001\u578b\u30ac\u30fc\u30c9\u3067\u7d5e\u308a\u8fbc\u3093\u3067\u304b\u3089\u64cd\u4f5c\u3059\u308b\u306e\u304c\u6b63\u3057\u3044\u30a2\u30d7\u30ed\u30fc\u30c1\u3067\u3059\u3002tsconfig.json<\/code>\u3067\"noImplicitAny\": true<\/code>\u3092\u8a2d\u5b9a\u3059\u308b\u3068\u3001\u6697\u9ed9\u7684\u306aany<\/code>\u578b\u3092\u30a8\u30e9\u30fc\u306b\u3067\u304d\u307e\u3059\u3002<\/p>\n\n\n\n
    \u5916\u90e8\u30e9\u30a4\u30d6\u30e9\u30ea\u306b\u578b\u5b9a\u7fa9\u304c\u306a\u3044\u5834\u5408\u306f\u3069\u3046\u3059\u308c\u3070\uff1f<\/h3>\n\n\n\n
    \u591a\u304f\u306e\u30e9\u30a4\u30d6\u30e9\u30ea\u306f@types\/\u30e9\u30a4\u30d6\u30e9\u30ea\u540d<\/code>\u3068\u3044\u3046\u30d1\u30c3\u30b1\u30fc\u30b8\u3067\u578b\u5b9a\u7fa9\u304c\u63d0\u4f9b\u3055\u308c\u3066\u3044\u307e\u3059\uff08DefinitelyTyped\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\uff09\u3002npm install --save-dev @types\/lodash<\/code>\u306e\u3088\u3046\u306b\u30a4\u30f3\u30b9\u30c8\u30fc\u30eb\u3059\u308b\u3060\u3051\u3067\u4f7f\u3048\u307e\u3059\u3002\u578b\u5b9a\u7fa9\u304c\u5b58\u5728\u3057\u306a\u3044\u5834\u5408\u306fdeclare module '\u30e9\u30a4\u30d6\u30e9\u30ea\u540d'<\/code>\u3067\u72ec\u81ea\u306b\u578b\u3092\u5b9a\u7fa9\u3059\u308b\u304b\u3001\u4e00\u6642\u7684\u306bany<\/code>\u578b\u3092\u4f7f\u3046\u3053\u3068\u3082\u3042\u308a\u307e\u3059\u3002<\/p>\n\n\n\n
    TypeScript\u306e\u30d3\u30eb\u30c9\u304c\u9045\u304f\u306a\u308a\u307e\u305b\u3093\u304b\uff1f<\/h3>\n\n\n\n
    Vite\u3084esbuild\u306fTypeScript\u306e\u30c8\u30e9\u30f3\u30b9\u30d1\u30a4\u30eb\u306e\u307f\u884c\u3044\u3001\u578b\u30c1\u30a7\u30c3\u30af\u3092\u30b9\u30ad\u30c3\u30d7\u3059\u308b\u305f\u3081\u975e\u5e38\u306b\u9ad8\u901f\u3067\u3059\u3002\u578b\u30c1\u30a7\u30c3\u30af\u306ftsc --noEmit<\/code>\u3092\u5225\u9014\u5b9f\u884c\u3059\u308b\u304b\u3001CI\u30d1\u30a4\u30d7\u30e9\u30a4\u30f3\u3067\u884c\u3046\u3053\u3068\u3067\u3001\u958b\u767a\u4f53\u9a13\u3068\u578b\u5b89\u5168\u6027\u3092\u4e21\u7acb\u3067\u304d\u307e\u3059\u3002tsconfig.json<\/code>\u3067\"isolatedModules\": true<\/code>\u3092\u8a2d\u5b9a\u3059\u308b\u3068Vite\u3068\u306e\u76f8\u6027\u3082\u5411\u4e0a\u3057\u307e\u3059\u3002<\/p>\n\n\n\n
    Generics\uff08\u30b8\u30a7\u30cd\u30ea\u30af\u30b9\uff09\u306f\u3044\u3064\u4f7f\u3048\u3070\u3044\u3044\u3067\u3059\u304b\uff1f<\/h3>\n\n\n\n
    \u578b\u306f\u9055\u3046\u304c\u51e6\u7406\u306e\u69cb\u9020\u304c\u540c\u3058\u95a2\u6570\u30fb\u30af\u30e9\u30b9\u3092\u66f8\u304f\u3068\u304d\u306b\u4f7f\u3044\u307e\u3059\u3002\u4f8b\u3048\u3070\u300c\u914d\u5217\u304b\u3089\u6700\u521d\u306e\u8981\u7d20\u3092\u53d6\u5f97\u3059\u308b\u95a2\u6570\u300d\u306ffunction first<T>(arr: T[]): T | undefined { return arr[0]; }<\/code>\u3068\u66f8\u3051\u3070\u3001\u6570\u5024\u914d\u5217\u3067\u3082\u6587\u5b57\u5217\u914d\u5217\u3067\u3082\u578b\u5b89\u5168\u306b\u52d5\u4f5c\u3057\u307e\u3059\u3002useState<User | null>(null)<\/code>\u306e\u3088\u3046\u306bReact\u3067\u65e5\u5e38\u7684\u306b\u4f7f\u3046\u5f62\u5f0f\u304c\u30b8\u30a7\u30cd\u30ea\u30af\u30b9\u3067\u3059\u3002<\/p>\n\n\n\n
    \n\n\n\n
    \u307e\u3068\u3081<\/h2>\n\n\n\n