ES6 Interview Questions for Freshers

ECMAScript 6, also known as ES6 or ECMAScript 2015, is the latest version of the ECMAScript language specification.

It was released in 2015 and introduced many new language features and syntax improvements to make JavaScript code more concise and easier to write. In this article, we will discuss some common interview questions related to ES6 that may be asked of freshers during a job interview. These questions will cover a range of topics related to ES6, including its new features, syntax, and usage.

By understanding these concepts, you can better prepare yourself for any ES6-related questions that may be asked during a job interview.

What is ECMAScript 6 (ES6)?

ECMAScript 6 (ES6) is the sixth major version of the ECMAScript language specification. It was released in 2015 and introduced a number of new language features and syntax improvements to make JavaScript code more concise and easier to write.

What are some of the new features introduced in ES6? Some of the new features introduced in ES6 include:

• Arrow functions
• Classes
• Modules
• Promises
• Generators
• Destructuring
• Default function parameters
• Rest and spread operators
• Map and set data structures

What is an arrow function in ES6?

An arrow function is a new syntax for defining functions in ES6. It uses the => operator to create a shorthand syntax for defining functions. For example, the following code defines a function add using the traditional function keyword:

function add(x, y) {
return x + y;
}

The same function can be defined using an arrow function as follows:

const add = (x, y) => {
return x + y;
}

What are classes in ES6?

ES6 introduces a new syntax for defining classes in JavaScript. A class is a blueprint for creating objects that share the same attributes and methods. For example, the following code defines a Person class with a constructor and a sayHello method:

class Person {
constructor(name) {
this.name = name;
}

sayHello() {
console.log(`Hello, my name is ${this.name}.`);
}
}

What are modules in ES6?

Modules in ES6 are pieces of code that can be imported and exported between different files. This allows for better code organization and separation of concerns. For example, the following code defines a Person class in one file and exports it:

// person.js
export class Person {
constructor(name) {
this.name = name;
}

sayHello() {
console.log(`Hello, my name is ${this.name}.`);
}
}

The Person class can then be imported and used in another file as follows:

// main.js
import { Person } from './person.js';

const person = new Person('John');
person.sayHello(); // Outputs: "Hello, my name is John."

function loadData() {
return new Promise((resolve, reject) => {
// Make an asynchronous request
setTimeout(() => {
const data = 'some data';
resolve(data);
}, 1000);
});
}

The loadData function can then be used as follows:

loadData().then((data) => {
// Do something with the data
});

What are generators in ES6?

Generators in ES6 are functions that can be paused and resumed. They allow for the creation of iterators with a new syntax using the * operator. Generators are typically used to implement complex iterators or asynchronous flows. For example, the following code defines a generator function counter that yields consecutive numbers:

function* counter() {
let i = 0;
while (true) {
yield i;
i++;
}
}

The counter function can be used as follows:

const iterator = counter();
console.log(iterator.next().value); // Outputs: 0
console.log(iterator.next().value); // Outputs: 1

What is destructuring in ES6?

Destructuring in ES6 is a new syntax for easily extracting data from arrays and objects. It allows for the creation of variables with the same names as the properties in an object or elements in an array. For example, the following code uses destructuring to extract the x and y properties from an object:

const point = { x: 1, y: 2 };
const { x, y } = point;
console.log(x); // Outputs: 1
console.log(y); // Outputs: 2

What are default function parameters in ES6?

Default function parameters in ES6 allow function arguments to be initialized with default values if no value or undefined is passed. This makes it possible to define optional parameters in functions. For example, the following code defines a calculateArea function with a default value for the width parameter:

function calculateArea(width = 1, height) {
return width * height;
}

console.log(calculateArea(2, 3)); // Outputs: 6
console.log(calculateArea(undefined, 3)); // Outputs: 3

What are the rest and spread operators in ES6?

The rest operator in ES6 is denoted by three dots (...) and allows for the representation of an indefinite number of arguments as an array. It is typically used to extract multiple arguments from a function call into an array. For example, the following code defines a logArguments function that uses the rest operator to log all of its arguments:

function logArguments(...args) {
console.log(args);
}

logArguments(1, 2, 3); // Outputs: [1, 2, 3]

const arr1 = [1, 2];
const arr2 = [3, 4];
const combined = [...arr1, ...arr2];
console.log(combined); // Outputs: [1, 2, 3, 4]