43:[{"uid":"1f3qm5k0kxz2","question":"Your authentication system needs to securely store user tokens. What's wrong with this implementation?","createdAt":"$D2025-01-05T19:37:02.458Z","updatedAt":"$D2025-01-31T22:40:38.455Z","questionDate":"","answerResource":null,"correctAnswer":"1f3qm5k0kxz0","codeSnippet":"

class TokenManager {\n  #tokens = new Map();\n  \n  constructor() {\n    this.checkTokens();\n    setInterval(this.checkTokens.bind(this), 60000);\n  }\n\n  async checkTokens() {\n    for (let [userId, tokenData] of this.#tokens) {\n      if (this.isExpired(tokenData)) {\n        this.#tokens.delete(userId);\n        await this.refreshToken(userId);\n      }\n    }\n  }\n\n  isExpired({ expiresAt }) {\n    return Date.now() >= expiresAt;\n  }\n\n  async refreshToken(userId) {\n    try {\n      const response = await fetch('/api/refresh', {\n        method: 'POST',\n        body: JSON.stringify({ userId })\n      });\n      const data = await response.json();\n      this.#tokens.set(userId, {\n        token: data.token,\n        expiresAt: Date.now() + data.expiresIn\n      });\n    } catch (error) {\n      console.error('Token refresh failed:', error);\n    }\n  }\n}

","hint":"Think about what happens if multiple tokens expire at the same time","dailyQuestion":false,"difficulty":"HARD","customQuestion":false,"slug":"security-issues-token-manager-implementation","slugGenerated":true,"description":null,"title":"Security Issues in Async Token Manager Implementation with Error Handling","questionType":"MULTIPLE_CHOICE","expectedParams":null,"functionName":null,"returnType":null,"testCases":null,"nextQuestionSlug":null,"previousQuestionSlug":null,"isPremiumQuestion":false},{"uid":"1f9sm69up9xh","question":"Enterprise-Grade Password Strength Validator","createdAt":"$D2025-01-23T21:34:27.462Z","updatedAt":"$D2025-01-31T22:40:38.455Z","questionDate":"","answerResource":null,"correctAnswer":"-","codeSnippet":"/**\n * Validates password strength based on enterprise-level security criteria\n * \n * @param {string} password - The password to validate\n * @returns {Object} Validation result with the following properties:\n * - isValid: Boolean indicating if password meets all security requirements\n * - strengthScore: Numerical score (0-5) representing password complexity\n * - feedback: Descriptive text about password strength\n * \n * @example\n * validatePassword(\"StrongPass123!\")\n * // Returns: { \n * isValid: true, \n * strengthScore: 4,\n * feedback: \"Strong password\"\n * }\n * \n * Security Checks:\n * - Minimum 12 characters\n * - Contains uppercase letters\n * - Contains lowercase letters\n * - Contains numbers\n * - Contains special characters\n * - Not in common password list\n */\nfunction validatePassword(password) {\n // Validation criteria implementation here\n}","hint":"Use regex to check character types Create a scoring system for password strength Check against a list of common passwords Return an object with validation details","dailyQuestion":false,"difficulty":"HARD","customQuestion":false,"slug":"password-strength-checker","slugGenerated":true,"description":"Develop a robust password validation function that enforces enterprise-level security standards for authentication systems.\n\n### Security Validation Criteria\n\nLength Requirements\n- Minimum 12 characters long\n- Ensures substantial password complexity\n\n### Complexity Dimensions\n\nMust contain at least:\n- One uppercase letter\n- One lowercase letter\n- One numeric character\n- One special character\n\n### Security Goals\n- Prevent weak credential selection\n- Mitigate common password vulnerabilities\n- Enhance authentication system resilience\n\n### Examples:\n```\nStrong Passwords:\n- StrongPass123!\n- C0mpl3x_P@ssw0rd\n\n❌ Weak Passwords:\n- short\n- onlyletters\n- NO_COMPLEXITY123\n```\n\n### Potential Use Cases\n\n- Financial platform authentication\n- Cloud service credential management\n- Enterprise security systems\n- User registration workflows","title":"Enterprise-Grade Password Strength Validator","questionType":"CODING_CHALLENGE","expectedParams":null,"functionName":null,"returnType":null,"testCases":[{"input":["StrongPass123!"],"expected":{"isValid":true,"feedback":"Excellent password","strengthScore":6}},{"input":["weak"],"expected":{"isValid":false,"feedback":"Moderate password","strengthScore":2}},{"input":["OnlyLetters"],"expected":{"isValid":false,"feedback":"Moderate password","strengthScore":3}},{"input":["C0mpl3x_P@ssw0rd"],"expected":{"isValid":true,"feedback":"Excellent password","strengthScore":6}}],"nextQuestionSlug":null,"previousQuestionSlug":null,"isPremiumQuestion":true},{"uid":"1p3dm5ww0hgp","question":"You're building a modern e-commerce platform that needs to fetch product data while handling loading and error states elegantly. The product team wants to implement React Suspense for a better user experience. How would you properly implement data fetching with Suspense while ensuring the code follows React 18's best practices and handles cache invalidation?","createdAt":"$D2025-01-14T19:50:09.764Z","updatedAt":"$D2025-01-31T22:40:38.455Z","questionDate":"","answerResource":null,"correctAnswer":"1p3dm5ww0hgl","codeSnippet":"$58","hint":"Think about how Suspense works with promises and what should happen during different states of the promise lifecycle. Consider how throwing promises is used in React's Suspense pattern.","dailyQuestion":false,"difficulty":"HARD","customQuestion":false,"slug":"implement-react-suspense-data-fetching-ecommerce","slugGenerated":true,"description":null,"title":"Dynamic Data Fetching with Suspense","questionType":"MULTIPLE_CHOICE","expectedParams":null,"functionName":null,"returnType":null,"testCases":null,"nextQuestionSlug":null,"previousQuestionSlug":null,"isPremiumQuestion":false},{"uid":"2258m5iopuxa","question":"Your team is building a real-time collaborative document editor. You need to implement a debounced auto-save function that prevents too many API calls while users are typing. What's missing in the code below to make it work correctly?","createdAt":"$D2025-01-04T21:17:10.218Z","updatedAt":"$D2025-01-31T22:40:38.455Z","questionDate":"2025-01-26","answerResource":null,"correctAnswer":"2258m5iopux7","codeSnippet":"

class DocumentEditor {\n    constructor() {\n        this.content = '';\n        this.lastSaved = null;\n        this.saveTimeout = null;\n    }\n\n    handleUserInput(newContent) {\n        this.content = newContent;\n        // Missing debounce implementation\n        _______________\n    }\n\n    async saveToServer() {\n        try {\n            await fetch('/api/save', {\n                method: 'POST',\n                body: JSON.stringify({ content: this.content }),\n                headers: { 'Content-Type': 'application/json' }\n            });\n            this.lastSaved = new Date();\n        } catch (error) {\n            console.error('Failed to save:', error);\n        }\n    }\n}

","hint":"Think about the difference between setTimeout and setInterval, and what happens to existing timeouts when new content arrives.","dailyQuestion":true,"difficulty":"HARD","customQuestion":false,"slug":"implement-debounced-autosave-collaborative-editor","slugGenerated":true,"description":null,"title":"Implementing Debounced Auto-Save in a Real-Time Collaborative Document Editor","questionType":"MULTIPLE_CHOICE","expectedParams":null,"functionName":null,"returnType":null,"testCases":null,"nextQuestionSlug":null,"previousQuestionSlug":null,"isPremiumQuestion":false},{"uid":"2258m5ioxyb8","question":"You're building a notification system for a chat application that needs to handle messages from multiple channels (email, SMS, push notifications). The system needs to process these notifications in order of priority but also handle failures gracefully. What's wrong with this implementation?","createdAt":"$D2025-01-04T21:23:27.856Z","updatedAt":"$D2025-01-31T22:40:38.455Z","questionDate":"","answerResource":null,"correctAnswer":"2258m5ioxyb7","codeSnippet":"$59","hint":"Think about race conditions and how the order of notifications might be affected by both the retry mechanism and concurrent additions.","dailyQuestion":false,"difficulty":"HARD","customQuestion":false,"slug":"fix-notification-system-queue-priority-error-handling","slugGenerated":true,"description":null,"title":"Fixing Race Conditions and Error Handling in Async Notification Queue System","questionType":"MULTIPLE_CHOICE","expectedParams":null,"functionName":null,"returnType":null,"testCases":null,"nextQuestionSlug":null,"previousQuestionSlug":null,"isPremiumQuestion":false},{"uid":"2258m5ips47j","question":"You're building a comment system where users can write, edit, and delete their comments. The system needs to prevent duplicate submissions and handle loading states. What's missing in this implementation?","createdAt":"$D2025-01-04T21:46:55.178Z","updatedAt":"$D2025-01-31T22:40:38.455Z","questionDate":"","answerResource":null,"correctAnswer":"2258m5ips47i","codeSnippet":"$5a","hint":"Think about data validation and cleanup after submission.","dailyQuestion":false,"difficulty":"MEDIUM","customQuestion":false,"slug":"react-comment-system-duplicate-submission-handling","slugGenerated":true,"description":null,"title":"How to Implement a React Comment System with Form Validation and Loading States","questionType":"MULTIPLE_CHOICE","expectedParams":null,"functionName":null,"returnType":null,"testCases":null,"nextQuestionSlug":null,"previousQuestionSlug":null,"isPremiumQuestion":false},{"uid":"2258m5iqic0o","question":"You're implementing a file upload component that needs to handle multiple files, show progress, and allow cancellation. What's wrong with this implementation?","createdAt":"$D2025-01-04T22:07:18.356Z","updatedAt":"$D2025-01-31T22:40:38.455Z","questionDate":"","answerResource":null,"correctAnswer":"2258m5iqic0l","codeSnippet":"$5b","hint":"Look at how the progress is tracked and what's missing from the upload request.","dailyQuestion":false,"difficulty":"HARD","customQuestion":false,"slug":"react-multiple-file-upload-progress-implementation-issues","slugGenerated":true,"description":null,"title":"React File Uploader: Fixing Multiple File Upload with Progress Tracking and Cancellation","questionType":"MULTIPLE_CHOICE","expectedParams":null,"functionName":null,"returnType":null,"testCases":null,"nextQuestionSlug":null,"previousQuestionSlug":null,"isPremiumQuestion":false},{"uid":"6flm5pae7hs","question":"Users of a weather dashboard application are reporting that sometimes the wrong city's weather is displayed. The following code is responsible for fetching and displaying weather data. What's the critical bug in this implementation?","createdAt":"$D2025-01-09T12:10:35.243Z","updatedAt":"$D2025-01-31T22:40:38.455Z","questionDate":"","answerResource":null,"correctAnswer":"6flm5pae7hr","codeSnippet":"

class WeatherDashboard extends React.Component {\n  state = {\n    weatherData: null,\n    selectedCity: null,\n    error: null\n  };\n\n  async fetchWeatherData(city) {\n    try {\n      const response = await fetch(\n        `https://api.weather.com/v1/${city}?apikey=12345`\n      );\n      const data = await response.json();\n      this.setState({\n        weatherData: data,\n        error: null\n      });\n    } catch (err) {\n      this.setState({ error: err.message });\n    }\n  }\n\n  handleCitySelect = (city) => {\n    this.setState({ selectedCity: city });\n    this.fetchWeatherData(city);\n  };\n\n  render() {\n    const { weatherData, error } = this.state;\n    return (\n      <div>\n        <CitySelector onSelect={this.handleCitySelect} />\n        {error ? (\n          <ErrorMessage message={error} />\n        ) : (\n          <WeatherDisplay data={weatherData} />\n        )}\n      </div>\n    );\n  }\n}

","hint":"Consider what happens when a user quickly switches between different cities before the previous API requests complete.","dailyQuestion":false,"difficulty":"HARD","customQuestion":false,"slug":"react-weather-dashboard-race-condition-bug","slugGenerated":true,"description":null,"title":"Fix Race Condition in React Weather Dashboard's API Calls","questionType":"MULTIPLE_CHOICE","expectedParams":null,"functionName":null,"returnType":null,"testCases":null,"nextQuestionSlug":null,"previousQuestionSlug":null,"isPremiumQuestion":false},{"uid":"9s7m5ibtoz1","question":"In a real-time chat application, you need to implement rate limiting for message sending. What will be the maximum number of messages a user can send in any 5-second window using this implementation?","createdAt":"$D2025-01-04T15:16:14.121Z","updatedAt":"$D2025-01-31T22:40:38.455Z","questionDate":"2025-01-09","answerResource":null,"correctAnswer":"9s7m5ibtoyy","codeSnippet":"$5c","hint":"Look at how the queue is cleaned and when new requests are allowed.","dailyQuestion":true,"difficulty":"HARD","customQuestion":false,"slug":"chat-rate-limit-messages-per-5-second-window","slugGenerated":true,"description":null,"title":"Implementing Message Rate Limiting in Real-Time Chat: Maximum 3 Messages per 5 Seconds","questionType":"MULTIPLE_CHOICE","expectedParams":null,"functionName":null,"returnType":null,"testCases":null,"nextQuestionSlug":null,"previousQuestionSlug":null,"isPremiumQuestion":false},{"uid":"9s7m5ic631m","question":"During a client meeting, your team discovers the authentication system isn't properly handling token expiration. What would be the output when testing this token validator?","createdAt":"$D2025-01-04T15:25:52.230Z","updatedAt":"$D2025-01-31T22:40:38.455Z","questionDate":"2025-01-11","answerResource":null,"correctAnswer":"9s7m5ic631k","codeSnippet":"

class TokenValidator {\n    constructor(expirationMinutes = 60) {\n        this.expirationMs = expirationMinutes * 60 * 1000;\n    }\n\n    createToken(userId) {\n        return {\n            userId,\n            created: Date.now(),\n            expires: Date.now() + this.expirationMs\n        };\n    }\n\n    isValid(token) {\n        if (!token?.expires) return false;\n        const now = Date.now();\n        const timeLeft = token.expires - now;\n        return timeLeft > 0;\n    }\n}\n\nconst validator = new TokenValidator(1); // 1 minute expiration\nconst token = validator.createToken('user123');\n\nsetTimeout(() => {\n    console.log(validator.isValid(token));\n}, 30 * 1000); // Check after 30 seconds\n\nsetTimeout(() => {\n    console.log(validator.isValid(token));\n}, 90 * 1000); // Check after 90 seconds

","hint":"Consider the time intervals and how they relate to the token's expiration time.","dailyQuestion":true,"difficulty":"EASY","customQuestion":false,"slug":"token-validator-expiration-timing-test","slugGenerated":true,"description":null,"title":"JavaScript Token Validation: Testing Authentication Token Expiration with setTimeout","questionType":"MULTIPLE_CHOICE","expectedParams":null,"functionName":null,"returnType":null,"testCases":null,"nextQuestionSlug":null,"previousQuestionSlug":null,"isPremiumQuestion":false}]