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React Js Developer Interview Questions

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538 react js developer interview questions shared by candidates

1. React fibre 2. Event Loop in JS, 3. Closure and hoisting. 4. Output based question. 5. Three DSA on arrays and string. 6. React query. 7. Typescript -> Why we use typescript, What is generics in TS, What is iterface in TS. 8.React hooks and there usecases. 9. Fetching the API in react and showing the result on react web UI. 10. Create one custom hook for fetch API. 11. What is specifity in CSS. 12. Sorting the result of API.
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React Js Developer

Interviewed at Calsoft

4.3★
Jan 17, 2025

1. React fibre 2. Event Loop in JS, 3. Closure and hoisting. 4. Output based question. 5. Three DSA on arrays and string. 6. React query. 7. Typescript -> Why we use typescript, What is generics in TS, What is iterface in TS. 8.React hooks and there usecases. 9. Fetching the API in react and showing the result on react web UI. 10. Create one custom hook for fetch API. 11. What is specifity in CSS. 12. Sorting the result of API.

Given a JSON data fetch out the "text" (key) value from it. And the JSON data is very complex. const assert = (result, expected) => { if (result.join(",") !== expected.join(",")) { throw "Error"; } else { console.log("Success"); } } const data = { id: "123", children: [ { id: "124", children: [], text: "Child 1" }, { id: "125", children: [], text: "Child 2" }, { id: "126", children: [ { id: "124", children: [], text: "Child 44" }, { id: "125", children: [], text: "Child 45" } ] } ], text: "Parent" }; let arr = []; const extractText = (childData) => { if(childData.text){ arr.push(childData.text); } if(childData.children.length > 0){ for(let i = 0; i < childData.children.length; i++){ extractText(childData.children[i]); } } } const flatten = (data) => { extractText(data); console.log(arr); return arr; } const expectedResult = ["Parent", "Child 1", "Child 2", "Child 44", "Child 45"]; assert(flatten(data), expectedResult); // This is the output which the function should return and it will match with the correct output ["Parent", "Child 1", "Child 2", "Child 44", "Child 45"];
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React Js Developer

Interviewed at 91social

4.3★
Dec 22, 2021

Given a JSON data fetch out the "text" (key) value from it. And the JSON data is very complex. const assert = (result, expected) => { if (result.join(",") !== expected.join(",")) { throw "Error"; } else { console.log("Success"); } } const data = { id: "123", children: [ { id: "124", children: [], text: "Child 1" }, { id: "125", children: [], text: "Child 2" }, { id: "126", children: [ { id: "124", children: [], text: "Child 44" }, { id: "125", children: [], text: "Child 45" } ] } ], text: "Parent" }; let arr = []; const extractText = (childData) => { if(childData.text){ arr.push(childData.text); } if(childData.children.length > 0){ for(let i = 0; i < childData.children.length; i++){ extractText(childData.children[i]); } } } const flatten = (data) => { extractText(data); console.log(arr); return arr; } const expectedResult = ["Parent", "Child 1", "Child 2", "Child 44", "Child 45"]; assert(flatten(data), expectedResult); // This is the output which the function should return and it will match with the correct output ["Parent", "Child 1", "Child 2", "Child 44", "Child 45"];

1. What is your internet speed 2. What spec is your laptop 3. Ask you to discuss some topic for English verification, 4. Show you a picture and ask you to describe what is happening in the picture 5. Written English verification, ask to listen to an audio about a conflict resolution, and write an email to the manager to describe the conflict and also an email to the conflict participants to discuss how to resolve it.
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React Js Developer

Interviewed at 1840 & Company

3.5★
Mar 8, 2025

1. What is your internet speed 2. What spec is your laptop 3. Ask you to discuss some topic for English verification, 4. Show you a picture and ask you to describe what is happening in the picture 5. Written English verification, ask to listen to an audio about a conflict resolution, and write an email to the manager to describe the conflict and also an email to the conflict participants to discuss how to resolve it.

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