e: string;\n// email: string;\n// }\n\n// For creating new users (no id yet)\ntype CreateUserDto = Omit;\n"}]}] 40:["$","hr","42",{"children":"$undefined"}] 41:["$","h2","44",{"children":"Record"}] 42:["$","p","46",{"children":"Creates an object type with specific key and value types."}] 43:["$","pre","48",{"children":["$","code",null,{"className":"language-typescript","children":"// Simple dictionary\ntype UserRoles = Record;\nconst roles: UserRoles = {\n admin: true,\n editor: false\n};\n\n// With union keys\ntype Status = 'pending' | 'approved' | 'rejected';\ntype StatusCounts = Record;\n\nconst counts: StatusCounts = {\n pending: 5,\n approved: 10,\n rejected: 2\n};\n\n// All keys must be present!\n"}]}] 44:["$","hr","50",{"children":"$undefined"}] 45:["$","h2","52",{"children":["Readonly",["$","t","1",{"children":"$undefined"}]]}] 46:["$","p","54",{"children":"Makes all properties read-only."}] 47:["$","pre","56",{"children":["$","code",null,{"className":"language-typescript","children":["interface User {\n id: number;\n name: string;\n}\n\ntype ImmutableUser = Readonly;\n\nconst user: ImmutableUser = { id: 1, name: 'Alice' };\nuser.name = 'Bob'; // ",["$","svg","1",{"ref":"$undefined","xmlns":"http://www.w3.org/2000/svg","width":24,"height":24,"viewBox":"0 0 24 24","fill":"none","stroke":"currentColor","strokeWidth":2,"strokeLinecap":"round","strokeLinejoin":"round","className":"lucide lucide-x inline-block w-5 h-5 text-red-500 align-text-bottom mr-1","aria-hidden":"true","children":[["$","path","1bl5f8",{"d":"M18 6 6 18"}],["$","path","d8bk6v",{"d":"m6 6 12 12"}],"$undefined"]}]," Error: Cannot assign to 'name'\n"]}]}] 48:["$","hr","58",{"children":"$undefined"}] 49:["$","h2","60",{"children":"Exclude and Extract"}] 4a:["$","pre","62",{"children":["$","code",null,{"className":"language-typescript","children":"type AllStatus = 'pending' | 'approved' | 'rejected' | 'cancelled';\n\n// Exclude — remove from union\ntype ActiveStatus = Exclude;\n// 'pending' | 'approved' | 'rejected'\n\n// Extract — keep only matching\ntype FinalStatus = Extract;\n// 'approved' | 'rejected'\n"}]}] 4b:["$","hr","64",{"children":"$undefined"}] 4c:["$","h2","66",{"children":["NonNullable",["$","t","1",{"children":"$undefined"}]]}] 4d:["$","p","68",{"children":"Removes null and undefined from a type."}] 4e:["$","pre","70",{"children":["$","code",null,{"className":"language-typescript","children":"type MaybeString = string | null | undefined;\n\ntype DefiniteString = NonNullable;\n// string\n\nfunction process(value: NonNullable) {\n // value is guaranteed to be string\n console.log(value.toUpperCase());\n}\n"}]}] 4f:["$","hr","72",{"children":"$undefined"}] 50:["$","h2","74",{"children":["ReturnType",["$","t","1",{"children":[" and Parameters",["$","t","1",{"children":"$undefined"}]]}]]}] 51:["$","pre","76",{"children":["$","code",null,{"className":"language-typescript","children":"function createUser(name: string, age: number): User {\n return { id: 1, name, age };\n}\n\n// Get return type of function\ntype UserResult = ReturnType;\n// User\n\n// Get parameters as tuple\ntype UserParams = Parameters;\n// [string, number]\n"}]}] 52:["$","hr","78",{"children":"$undefined"}] 53:["$","h2","80",{"children":"Combining Utility Types"}] 54:["$","pre","82",{"children":["$","code",null,{"className":"language-typescript","children":"interface User {\n id: number;\n name: string;\n email: string;\n password: string;\n createdAt: Date;\n}\n\n// Create DTO: no id (generated), password required\ntype CreateUserDto = Omit;\n\n// Update DTO: all optional except id\ntype UpdateUserDto = Partial> & Pick;\n\n// Public profile: no sensitive data, readonly\ntype PublicProfile = Readonly>;\n"}]}] 55:["$","hr","84",{"children":"$undefined"}] 56:["$","h2","86",{"children":"Related Topics