[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"me":3,"catalog:en:frontend\u002Ftypescript-type-fundamentals":4,"config":235},null,{"field_key":5,"field_name":6,"seniority":7,"topic_key":8,"topic_name":9,"spec_key":7,"spec_name":7,"locale":10,"cell_total":11,"field_total":12,"seniorities":13,"topics":17,"specs":133,"samples":150},"frontend","Frontend","","typescript-type-fundamentals","Typescript Type Fundamentals","en",75,2925,[14,15,16],"junior","mid","senior",[18,21,24,27,30,33,36,39,42,45,48,51,54,57,60,63,66,69,72,75,78,81,84,87,90,93,96,99,102,105,108,111,112,115,118,121,124,127,130],{"key":19,"name":20,"count":11},"accessibility","Accessibility",{"key":22,"name":23,"count":11},"angular-change-detection","Angular Change Detection",{"key":25,"name":26,"count":11},"angular-components-lifecycle","Angular Components Lifecycle",{"key":28,"name":29,"count":11},"angular-dependency-injection","Angular Dependency Injection",{"key":31,"name":32,"count":11},"angular-directives-pipes","Angular Directives Pipes",{"key":34,"name":35,"count":11},"angular-router-forms","Angular Router Forms",{"key":37,"name":38,"count":11},"angular-testing-performance","Angular Testing Performance",{"key":40,"name":41,"count":11},"css-layout","Css Layout",{"key":43,"name":44,"count":11},"dom-browser-apis","Dom Browser Apis",{"key":46,"name":47,"count":11},"javascript-async-concurrency","Javascript Async Concurrency",{"key":49,"name":50,"count":11},"javascript-language","Javascript Language",{"key":52,"name":53,"count":11},"javascript-memory-performance","Javascript Memory Performance",{"key":55,"name":56,"count":11},"javascript-modules-bundling","Javascript Modules Bundling",{"key":58,"name":59,"count":11},"javascript-prototypes-oop","Javascript Prototypes Oop",{"key":61,"name":62,"count":11},"javascript-runtime-apis","Javascript Runtime Apis",{"key":64,"name":65,"count":11},"javascript-testing-tooling","Javascript Testing Tooling",{"key":67,"name":68,"count":11},"performance","Performance",{"key":70,"name":71,"count":11},"react-components-jsx","React Components Jsx",{"key":73,"name":74,"count":11},"react-context-state","React Context State",{"key":76,"name":77,"count":11},"react-effects-lifecycle","React Effects Lifecycle",{"key":79,"name":80,"count":11},"react-forms-suspense","React Forms Suspense",{"key":82,"name":83,"count":11},"react-hooks-state","React Hooks State",{"key":85,"name":86,"count":11},"react-rendering-performance","React Rendering Performance",{"key":88,"name":89,"count":11},"rendering-reactivity","Rendering Reactivity",{"key":91,"name":92,"count":11},"state-management","State Management",{"key":94,"name":95,"count":11},"testing","Testing",{"key":97,"name":98,"count":11},"typescript-advanced-types","Typescript Advanced Types",{"key":100,"name":101,"count":11},"typescript-generics","Typescript Generics",{"key":103,"name":104,"count":11},"typescript-modules-declarations","Typescript Modules Declarations",{"key":106,"name":107,"count":11},"typescript-narrowing-control-flow","Typescript Narrowing Control Flow",{"key":109,"name":110,"count":11},"typescript-tooling-config","Typescript Tooling Config",{"key":8,"name":9,"count":11},{"key":113,"name":114,"count":11},"vue-components-props","Vue Components Props",{"key":116,"name":117,"count":11},"vue-composition-api","Vue Composition Api",{"key":119,"name":120,"count":11},"vue-directives-templates","Vue Directives Templates",{"key":122,"name":123,"count":11},"vue-performance-testing","Vue Performance Testing",{"key":125,"name":126,"count":11},"vue-reactivity-system","Vue Reactivity System",{"key":128,"name":129,"count":11},"vue-router-state-management","Vue Router State Management",{"key":131,"name":132,"count":11},"web-security","Web Security",[134,138,141,144,147],{"key":135,"name":136,"count":137},"angular","Angular",450,{"key":139,"name":140,"count":137},"javascript","JavaScript",{"key":142,"name":143,"count":137},"react","React",{"key":145,"name":146,"count":137},"typescript","TypeScript",{"key":148,"name":149,"count":137},"vue","Vue",[151,169,183,196,209,222],{"id":152,"topic":9,"difficulty":153,"body":154,"options":155,"correct_key":160,"explanation":168},"019f7611-bd68-73a0-b2b4-caee8383ec8a",1,"In TypeScript, what is the main similarity between `interface` and `type` alias when describing the shape of an object?",[156,159,162,165],{"key":157,"text":158},"a","Only `interface` can describe an object's shape; `type` is for primitives only",{"key":160,"text":161},"b","Both can describe an object's shape with named properties and types",{"key":163,"text":164},"c","Only `type` can describe an object's shape; `interface` is for classes only",{"key":166,"text":167},"d","Neither can describe object shapes; both are limited to function signatures","Both `interface` and `type` alias can describe an object's shape (named properties with types) — this is their core overlapping use case. They differ in other capabilities (declaration merging, unions, etc.), covered in later questions, but describing object shape is something both do.",{"id":170,"topic":9,"difficulty":171,"body":172,"options":173,"correct_key":163,"explanation":182},"019f7611-bd68-7b42-a979-1b2496dba3d5",2,"```typescript\nlet id: string | number;\nid = \"abc\";\nid = 42;\nid = true;\n```\nWhich line causes a TypeScript compile error?",[174,176,178,180],{"key":157,"text":175},"`id = \"abc\";` — string is not allowed here",{"key":160,"text":177},"`id = 42;` — number is not allowed here",{"key":163,"text":179},"`id = true;`",{"key":166,"text":181},"None of the lines cause an error","`id`'s type is the union `string | number` — only values of type `string` or `number` are assignable. `\"abc\"` and `42` both fit, but `true` is a `boolean`, which is not one of the allowed union members, so it's a type error.",{"id":184,"topic":9,"difficulty":153,"body":185,"options":186,"correct_key":166,"explanation":195},"019f7611-bd69-7304-a2f0-72eb5e4b1db4","```typescript\ntype Direction = \"up\" | \"down\" | \"left\" | \"right\";\nlet move: Direction = \"up\";\nmove = \"diagonal\";\n```\nWhat happens on the last line?",[187,189,191,193],{"key":157,"text":188},"It compiles fine, `Direction` accepts any string",{"key":160,"text":190},"It compiles fine, but `move` becomes `undefined` at runtime",{"key":163,"text":192},"It throws a `TypeError` when the code runs",{"key":166,"text":194},"TypeScript compile error — `\"diagonal\"` isn't a valid `Direction` literal","`Direction` is a union of specific string literal types. Only exactly `\"up\"`, `\"down\"`, `\"left\"`, or `\"right\"` are assignable to a variable of that type. `\"diagonal\"` is a valid `string`, but not one of those literals, so the compiler rejects the assignment — this is a compile-time error, not a runtime one, since TypeScript's types don't exist after compilation.",{"id":197,"topic":9,"difficulty":171,"body":198,"options":199,"correct_key":157,"explanation":208},"019f7611-bd69-7b1a-960c-3d554792ce0c","```typescript\ninterface Point {\n  readonly x: number;\n  readonly y: number;\n}\nconst p: Point = { x: 1, y: 2 };\np.x = 5;\n```\nWhat happens on the last line?",[200,202,204,206],{"key":157,"text":201},"TypeScript compile error — `x` is `readonly`",{"key":160,"text":203},"It compiles and runs fine, `p.x` becomes `5`",{"key":163,"text":205},"It throws a runtime `TypeError` because `p` was declared with `const`",{"key":166,"text":207},"It compiles fine but `p.x` silently stays `1`","`readonly` on an interface property means it can only be set once, when the object is created (or in a constructor for classes) — any later assignment is a compile-time error. This is unrelated to `const` on the variable (which only prevents reassigning `p` itself, not its properties).",{"id":210,"topic":9,"difficulty":153,"body":211,"options":212,"correct_key":163,"explanation":221},"019f7611-bd6a-73c0-bad0-9b6942dcc7d1","```typescript\ninterface User {\n  name: string;\n  nickname?: string;\n}\n```\nWhat does the `?` after `nickname` mean?",[213,215,217,219],{"key":157,"text":214},"`nickname` must always be `null`",{"key":160,"text":216},"`nickname` can be any type, not just `string`",{"key":163,"text":218},"`nickname` is optional, may be omitted",{"key":166,"text":220},"`nickname` is computed automatically from `name`","The `?` marks a property as optional: a value of type `User` is valid whether or not it includes `nickname`. If present, it must still be a `string`; TypeScript effectively treats its type as `string | undefined` when accessed.",{"id":223,"topic":9,"difficulty":171,"body":224,"options":225,"correct_key":160,"explanation":234},"019f7611-bd6a-7bbb-8f93-1df8a53bd4ef","```typescript\ninterface Named { name: string; }\n\nfunction greet(x: Named) {\n  return `Hi, ${x.name}`;\n}\n\nclass Dog {\n  name: string = \"Rex\";\n  breed: string = \"Lab\";\n}\n\ngreet(new Dog());\n```\nDoes `greet(new Dog())` compile, and why?",[226,228,230,232],{"key":157,"text":227},"No, because `Dog` doesn't explicitly `implements Named`",{"key":160,"text":229},"Yes, TypeScript uses structural typing — shape match is enough",{"key":163,"text":231},"No, because `Dog` has an extra property (`breed`) not declared in `Named`",{"key":166,"text":233},"Yes, but only because `Dog` and `Named` share the same file","TypeScript's type system is structural (duck typing), not nominal: a type is compatible if its shape matches, regardless of explicit `implements`\u002F`extends` declarations or naming. `Dog` has a `name: string`, which is all `Named` requires — the extra `breed` property doesn't disqualify it, since having more is fine when passing a variable (as opposed to an object literal, which is checked more strictly for excess properties).",{"fields":236,"seniorities":410,"interview_shapes":411,"locales":416,"oauth":418,"question_count":421,"coach_enabled":422,"jd_match_enabled":422},[237,262,270,287,311,324,343,362,384,391,397,404],{"key":238,"name_tr":239,"name_en":239,"sort":153,"specializations":240},"backend","Backend",[241,244,247,250,253,256,259],{"key":242,"name":243,"field":238},"general","Genel",{"key":245,"name":246,"field":238},"go","Go",{"key":248,"name":249,"field":238},"python","Python",{"key":251,"name":252,"field":238},"java","Java",{"key":254,"name":255,"field":238},"csharp","C#\u002F.NET",{"key":257,"name":258,"field":238},"nodejs","Node.js",{"key":260,"name":261,"field":238},"php","PHP",{"key":5,"name_tr":6,"name_en":6,"sort":171,"specializations":263},[264,265,266,267,268,269],{"key":242,"name":243,"field":5},{"key":139,"name":140,"field":5},{"key":145,"name":146,"field":5},{"key":142,"name":143,"field":5},{"key":148,"name":149,"field":5},{"key":135,"name":136,"field":5},{"key":271,"name_tr":272,"name_en":272,"sort":273,"specializations":274},"fullstack","Fullstack",3,[275,276,277,278,279,280,281,282,283,284,285,286],{"key":242,"name":243,"field":271},{"key":245,"name":246,"field":238},{"key":248,"name":249,"field":238},{"key":251,"name":252,"field":238},{"key":254,"name":255,"field":238},{"key":257,"name":258,"field":238},{"key":260,"name":261,"field":238},{"key":139,"name":140,"field":5},{"key":145,"name":146,"field":5},{"key":142,"name":143,"field":5},{"key":148,"name":149,"field":5},{"key":135,"name":136,"field":5},{"key":288,"name_tr":289,"name_en":289,"sort":290,"specializations":291},"devops-cloud","DevOps 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