You cannot shadow a let variable with a var variable within the same block scope. Doing so throws a syntax error because var tries to escape the block and attach to the function or global scope, causing a naming collision. 5. Asynchronous JavaScript and the Event Loop
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function debounce(func, delay) let timer; return function(...args) const context = this; clearTimeout(timer); timer = setTimeout(() => func.apply(context, args); , delay); ; Use code with caution. Section 4: Object-Oriented and Functional Programming 8. Explain Prototype Inheritance. happy rawat javascript interview questions pdf free best
: Objects representing the eventual completion or failure of an asynchronous operation. They prevent "callback hell" through chaining ( .then() , .catch() ).
When you access a property, JavaScript searches the object itself. If it cannot find it, it searches the prototype, climbing up the chain until it hits null . 3. The Event Loop, Microtasks, and Macrotasks You cannot shadow a let variable with a
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console.log(a); // Outputs: undefined due to hoisting var a = 5; console.log(b); // Throws ReferenceError: Cannot access 'b' before initialization let b = 10; Use code with caution. 2. Advanced Functions and Scoping
Introduced in ES6. Variables declared with let and const stay inside the curly braces {} where they are defined.
Asynchronous execution is the backbone of modern web applications. The Event Loop Architecture