What is the difference between var , let , and const ?Var is function-scoped and hoisted. Let and const are block-scoped. Const prevents reassignment, while let allows it.
Quiz yourself. Cover the answers and try to recall them. Then, find a friend or use a mock-interview tool to practice answering these questions under simulated pressure. Focus on communicating your thought process clearly.
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: Arrow functions, destructuring, spread/rest operators, and template literals.
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The is a mechanism the engine uses to keep track of its place in a script that calls multiple functions. It operates on a Last In, First Out (LIFO) principle. When a function is called, it is pushed onto the stack. When it finishes executing, it is popped off. Hoisting: Temporal Dead Zone (TDZ)
Promises and MutationObserver callbacks go to the Microtask Queue, which has higher priority than the Callback Queue (Macrotasks).
Closures are automatically created every time a function is defined inside another function. Real-World Use Case: Data Encapsulation / Private Variables What is the difference between var , let , and const
7. Explain the Event Loop, Microtask Queue, and Macrotask Queue.
function createCounter() let count = 0; // This variable is "private" return function() count++; return count; ;
Happy Rawat is a well-known technical educator and content creator, highly regarded in the web development community for his practical, interview-focused JavaScript tutorials. His curated question sets specifically target the core mechanics and modern quirks of JavaScript that top-tier tech companies frequently test.
Objects inherit directly from other objects via a prototype chain. Every JavaScript object has a hidden private property ( [[Prototype]] ) linking to another object. Even modern JavaScript class syntax is just syntactic sugar over prototypal inheritance. Q4: How do call() , apply() , and bind() differ? Quiz yourself
Handles lower-priority callbacks like setTimeout , setInterval , and DOM events.
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function createCounter() let count = 0; return function() count++; return count; ; const counter = createCounter(); console.log(counter()); // Output: 1 console.log(counter()); // Output: 2 Use code with caution. The Event Loop
What is the difference between Call, Apply, and Bind?Call invokes a function with a specific this . Apply is the same but takes arguments as an array. Bind returns a new function.