Interview Q&A

Short answer: The constructor is a special method for initializing new objects created from a class. Example: class Car { constructor(brand, model) { this.brand = brand; this.model = model; } }

Example code

The constructor is a special method for initializing new objects created from a class. Example: class Car { constructor(brand, model) { this.brand = brand;
this.model = model;
}
}

Real-world example (ShopNest)

In ShopNest’s cart UI, a click handler closes over productId. Use let in loops so each button keeps the correct id.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Feature Function Constructor Class Syntax function Person(){} class Person{} Hoisting Yes, function declarations are hoisted No, classes are not hoisted new required Recommended Required

Real-world example (ShopNest)

In ShopNest’s cart UI, a click handler closes over productId. Use let in loops so each button keeps the correct id.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Classes support extends to create a subclass that inherits properties and methods from a parent class. Example: class Animal { speak() { console.log("Animal speaks"); } } class Dog extends Animal { speak() { console.log("Dog barks"); } } const dog = new Dog(); dog.speak(); // Dog barks

Example code

Classes support extends to create a subclass that inherits properties and methods from a parent class. Example: class Animal { speak() { console.log("Animal speaks"); } }
class Dog extends Animal { speak() { console.log("Dog barks"); } }
const dog = new Dog(); dog.speak(); // Dog barks

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: super() calls the parent class constructor. Must be called before using this in subclass. Example: class Animal {

Example code

constructor(name) { this.name = name; }
}
class Dog extends Animal { constructor(name, breed) { super(name); this.breed = breed;
}
}

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Static methods are called on the class itself, not on instances.

Example code

class MathUtils { static square(x) { return x * x; } } console.log(MathUtils.square(5)); // 25

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Yes, getters and setters control access to object properties. Example: class Person {

Example code

constructor(name) { this._name = name; } get name() { return this._name; } set name(value) { this._name = value; }
}
const p = new Person("Sandeep"); console.log(p.name); // Sandeep p.name = "Ravi"; console.log(p.name); // Ravi

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Allows non-blocking execution, letting other code run while waiting for tasks (e.g., network requests).

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Functions passed as arguments to run after another function completes. Example: setTimeout(() => console.log("Hello after 1s"), 1000);

Example code

Functions passed as arguments to run after another function completes. Example: setTimeout(() => console.log("Hello after 1s"), 1000);

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Nested callbacks causing hard-to-read code. Solution: Use Promises or async/await.

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: n object representing future completion or failure of an async task.

Real-world example (ShopNest)

The checkout button uses async/await to call /api/orders, shows a spinner, and catches network errors with a toast.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: pending fulfilled rejected

Real-world example (ShopNest)

The checkout button uses async/await to call /api/orders, shows a spinner, and catches network errors with a toast.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: fetch('/api/data') .then(res => res.json()) .then(data => console.log(data)) .catch(err => console.error(err));

Example code

fetch('/api/data') .then(res => res.json()) .then(data => console.log(data)) .catch(err => console.error(err));

Real-world example (ShopNest)

The checkout button uses async/await to call /api/orders, shows a spinner, and catches network errors with a toast.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: sync function fetchData() { try { const res = await fetch('/api/data'); const data = await res.json(); console.log(data); } catch (err) { console.error(err); } } sync function fetchData() { try { const res = await fetch('/api/data'); const data = await res.json(); console.log(data); } catch (err) { console.error(err); } }… sync function fetchData() { try {… const res = await fetch('/api/data'); const data = await…

Explain a bit more

res.json(); console.log(data); } catch (err) { console.error(err); } } sync function fetchData() { try { const res = await fetch('/api/data'); const data = await res.json(); console.log(data); } catch (err) { console.error(err); } }…

Real-world example (ShopNest)

The checkout button uses async/await to call /api/orders, shows a spinner, and catches network errors with a toast.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Syntactic sugar over Promises for cleaner asynchronous code. async function fetchData() { try { const res = await fetch('/api/data'); const data = await res.json(); console.log(data); } catch (err) { console.error(err); } }

Example code

Syntactic sugar over Promises for cleaner asynchronous code. async function fetchData() { try { const res = await fetch('/api/data');
const data = await res.json(); console.log(data); } catch (err) { console.error(err); } }

Real-world example (ShopNest)

The checkout button uses async/await to call /api/orders, shows a spinner, and catches network errors with a toast.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Promise.all – waits for all promises to resolve Promise.race – resolves/rejects as soon as one completes

Real-world example (ShopNest)

The checkout button uses async/await to call /api/orders, shows a spinner, and catches network errors with a toast.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Mechanism that manages async callbacks and executes them after the call stack is empty.

Real-world example (ShopNest)

The checkout button uses async/await to call /api/orders, shows a spinner, and catches network errors with a toast.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Call stack: executes synchronous code Microtask queue: handles Promises Macrotask queue: handles setTimeout, I/O, etc.

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: n action like click, load, input, keypress.

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: button.addEventListener('click', () => console.log('Clicked!')); button.addEventListener('click', () => console.log('Clicked!')); button.addEventListener('click', () => console.log('Clicked!')); button.addEventListener('click', () => console.log('Clicked!'));

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: ttach a listener to a parent to handle events on child elements.

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: preventDefault() – stops default browser action stopPropagation() – stops event bubbling

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Catching and managing runtime errors to prevent app crashes.

Explain a bit more

Catching and managing runtime errors to prevent app crashes. Catching and managing runtime errors to prevent app crashes. Catching and managing runtime errors to prevent app crashes. Catching and managing runtime errors to prevent app crashes. Catching and managing runtime errors to prevent app crashes. Catching and managing runtime errors to prevent app crashes. Catching and managing runtime errors to prevent app crashes.

Example code

Catching and managing runtime errors to prevent app crashes. Catching and managing runtime errors to prevent app crashes. Catching and managing runtime errors to prevent app crashes. Catching and managing runtime errors to prevent app crashes. Catching and managing runtime errors to prevent app crashes. Catching and managing runtime errors to prevent app crashes. Catching and managing runtime errors to prevent app crashes. Catching and managing runtime errors to prevent app crashes.

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Blocks to handle exceptions. try { JSON.parse("invalid"); } catch(e) { console.error(e); }

Example code

Blocks to handle exceptions. try { JSON.parse("invalid"); } catch(e) { console.error(e); }

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Runs always, whether error occurs or not.

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: class ValidationError extends Error { } throw new ValidationError("Invalid input");

Example code

class ValidationError extends Error { } throw new ValidationError("Invalid input");

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.