Interview Q&A

Short answer: Creates a new object with the specified prototype object. Example: const parent = { greet() { console.log("Hello"); } }; const child = Object.create(parent); child.greet(); // Hello

Example code

Creates a new object with the specified prototype object. Example: const parent = { greet() { console.log("Hello"); } };
const child = Object.create(parent); child.greet(); // Hello

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: property of functions, used when creating objects with new.

Explain a bit more

__proto __ property of objects, points to the object’s prototype (used in the prototype chain). property of functions, used when creating objects with new. __proto __ property of objects, points to the object’s prototype (used in the prototype chain). property of functions, used when creating objects with new. __proto __ property of objects, points to the object’s prototype (used in the prototype chain). function Person() {} console.log(Person.prototype); // prototype object const p = new Person(); console.log(p.__proto__); // same as Person.prototype property of functions, used when creating objects with new. __proto __ property of objects, points to the object’s prototype (used in the prototype chain).

Example code

function Person() {} console.log(Person.prototype); // prototype object const p = new Person(); console.log(p.__proto__); // same as Person.prototype

Real-world example (ShopNest)

Prefer arrow functions for React/event callbacks in ShopNest so this is not accidentally rebound.

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: Property Description prototy pe A property of functions, used when creating objects with new. __proto __ A property of objects, points to the object’s prototype (used in the prototype chain).

Example code

function Person() {} console.log(Person.prototype); // prototype object const p = new Person(); console.log(p.__proto__); // same as Person.prototype

Real-world example (ShopNest)

Prefer arrow functions for React/event callbacks in ShopNest so this is not accidentally rebound.

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 are blueprints for creating objects. They provide syntactic sugar over the traditional prototype-based inheritance. Example: class Person { constructor(name, age) { this.name = name;

Example code

this.age = age;
}
}
const sandeep = new Person("Sandeep", 30); console.log(sandeep.name); // Sandeep

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: 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.