[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"me":3,"catalog:en:frontend\u002Fjavascript-language":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","","javascript-language","Javascript Language","en",75,2925,[14,15,16],"junior","mid","senior",[18,21,24,27,30,33,36,39,42,45,48,49,52,55,58,61,64,67,70,73,76,79,82,85,88,91,94,97,100,103,106,109,112,115,118,121,124,127,130],{"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":8,"name":9,"count":11},{"key":50,"name":51,"count":11},"javascript-memory-performance","Javascript Memory Performance",{"key":53,"name":54,"count":11},"javascript-modules-bundling","Javascript Modules Bundling",{"key":56,"name":57,"count":11},"javascript-prototypes-oop","Javascript Prototypes Oop",{"key":59,"name":60,"count":11},"javascript-runtime-apis","Javascript Runtime Apis",{"key":62,"name":63,"count":11},"javascript-testing-tooling","Javascript Testing Tooling",{"key":65,"name":66,"count":11},"performance","Performance",{"key":68,"name":69,"count":11},"react-components-jsx","React Components Jsx",{"key":71,"name":72,"count":11},"react-context-state","React Context State",{"key":74,"name":75,"count":11},"react-effects-lifecycle","React Effects Lifecycle",{"key":77,"name":78,"count":11},"react-forms-suspense","React Forms Suspense",{"key":80,"name":81,"count":11},"react-hooks-state","React Hooks State",{"key":83,"name":84,"count":11},"react-rendering-performance","React Rendering Performance",{"key":86,"name":87,"count":11},"rendering-reactivity","Rendering Reactivity",{"key":89,"name":90,"count":11},"state-management","State Management",{"key":92,"name":93,"count":11},"testing","Testing",{"key":95,"name":96,"count":11},"typescript-advanced-types","Typescript Advanced Types",{"key":98,"name":99,"count":11},"typescript-generics","Typescript Generics",{"key":101,"name":102,"count":11},"typescript-modules-declarations","Typescript Modules Declarations",{"key":104,"name":105,"count":11},"typescript-narrowing-control-flow","Typescript Narrowing Control Flow",{"key":107,"name":108,"count":11},"typescript-tooling-config","Typescript Tooling Config",{"key":110,"name":111,"count":11},"typescript-type-fundamentals","Typescript Type Fundamentals",{"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":157,"explanation":168},"019f56bb-ba72-7e75-a41e-768daf63734c",1,"In JavaScript, what is the main difference between `let` and `const`?",[156,159,162,165],{"key":157,"text":158},"a","A `const` binding cannot be reassigned after its initial assignment",{"key":160,"text":161},"b","A `const` variable is only accessible inside the function that declares it",{"key":163,"text":164},"c","A `let` variable is not hoisted, while a `const` variable is",{"key":166,"text":167},"d","A `const` also prevents the contents of an object or array from changing","`const` forbids reassigning the binding itself, while `let` allows reassignment; both are block-scoped, so (b) is wrong. `const` does not freeze the value it points to — the properties of a `const` object can still be mutated, which makes (d) a very common misconception.",{"id":170,"topic":9,"difficulty":171,"body":172,"options":173,"correct_key":163,"explanation":182},"019f56bb-ba73-750f-a83f-b2fdb59103d4",2,"```\nconsole.log(a);\nconsole.log(b);\nvar a = 1;\nlet b = 2;\n```\nWhat happens when this code runs?",[174,176,178,180],{"key":157,"text":175},"It prints `undefined` and then `undefined`",{"key":160,"text":177},"It prints `1` and then `2`",{"key":163,"text":179},"It prints `undefined`, then throws a ReferenceError for `b`",{"key":166,"text":181},"It throws a ReferenceError on the very first line","`var a` is hoisted and initialized to `undefined`, so reading `a` before its assignment prints `undefined`. `let b` is hoisted too but stays in the temporal dead zone until its declaration, so reading it early throws a ReferenceError. Because `a` is logged first and succeeds, the error is not on the first line (d).",{"id":184,"topic":9,"difficulty":171,"body":185,"options":186,"correct_key":160,"explanation":195},"019f56bb-ba73-7aa4-b63f-9ca25c53b315","```\nfunction makeCounter() {\n  let count = 0;\n  return function () {\n    count += 1;\n    return count;\n  };\n}\nconst next = makeCounter();\nconsole.log(next(), next(), next());\n```\nWhat does this print?",[187,189,191,193],{"key":157,"text":188},"`1 1 1`, because `count` resets to 0 on every call",{"key":160,"text":190},"`1 2 3`, because the inner function still sees the same `count`",{"key":163,"text":192},"`0 1 2`, because `count` is returned before it is incremented",{"key":166,"text":194},"It throws, because `count` is not defined inside the inner function","`makeCounter` returns an inner function that closes over `count`; that variable lives on between calls instead of resetting, so the three calls yield 1, 2, 3. The increment happens before `return`, so it never prints 0 first (c), and closure is exactly why `count` is still visible inside (d).",{"id":197,"topic":9,"difficulty":171,"body":198,"options":199,"correct_key":166,"explanation":208},"019f56bb-ba74-70ed-ad34-5b880cded04c","In a regular (non-arrow) function called as `obj.method()`, what does `this` refer to?",[200,202,204,206],{"key":157,"text":201},"The global object, regardless of how the function is called",{"key":160,"text":203},"The function object itself",{"key":163,"text":205},"Whatever value was passed as the first argument to the function",{"key":166,"text":207},"The object the method was called on — here, `obj`","For a regular function, `this` is set by the call site; calling it as a method binds `this` to the object left of the dot. When the same function is called plain (not as a method), `this` falls back to the global object or `undefined` in strict mode — which is why (a) is only true for that unbound case.",{"id":210,"topic":9,"difficulty":171,"body":211,"options":212,"correct_key":160,"explanation":221},"019f56bb-ba74-7577-8eb4-be803d205d0a","```\nconsole.log(0 == '');\nconsole.log(0 == '0');\nconsole.log('' == '0');\n```\nWhat does this print, in order?",[213,215,217,219],{"key":157,"text":214},"`true`, `true`, `true`",{"key":160,"text":216},"`true`, `true`, `false`",{"key":163,"text":218},"`false`, `false`, `false`",{"key":166,"text":220},"`true`, `false`, `false`","With `==`, both sides are coerced to numbers when comparing a number to a string: `0 == ''` becomes `0 == 0` (true) and `0 == '0'` becomes `0 == 0` (true). But `'' == '0'` compares two strings directly, with no coercion, so it is `false`. Using `===` would make all three `false` because the types differ.",{"id":223,"topic":9,"difficulty":171,"body":224,"options":225,"correct_key":163,"explanation":234},"019f56bb-ba74-7aa4-9072-cb23d6b2ba74","Why do many JavaScript style guides recommend using `===` instead of `==`?",[226,228,230,232],{"key":157,"text":227},"`===` is faster because it does not have to read the right-hand operand at all",{"key":160,"text":229},"`==` is deprecated and will be removed from the language",{"key":163,"text":231},"`===` compares without type coercion, so results are more predictable",{"key":166,"text":233},"`===` can compare objects by their contents, while `==` cannot","`==` applies type coercion rules that are easy to get wrong (for example `0 == ''` is true), while `===` requires both the type and the value to match, avoiding surprises. `==` is not deprecated (b), and neither operator compares objects by content — both compare object references (d).",{"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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