ES6 Interview Questions

ES6 stands for ECMAScript 6. ECMAScript was created to standardise JavaScript, and ES6 is the 6th version of ECMAScript, it was published in 2015, and is also known as ECMAScript 2015.

This is one of the essential skills of programmer now a days. Either front end or Back-end both of the development work are depend on JavaScript and ES6 is becoming backbone of the applications now a days.

The huge demand of ES6 required huge number of developers in almost the companies like IBM, Hot Star, HCL, TCS. You will find here ES6 Interview Questions and their solutions.

What is ES6 or What is ECMAScript?

ECMAScript 6 is also known as ES6 and ECMAScript 2015 or Simply JavaScript 6. ES6 is new version of JavaScript and having many new features. The new features of ES6 making JavaScript a New Age Scripting language.

The ES6 is the sixth edition of the language and was released on June 2015. It was initally known as ECMAScript 6 (ES6) and later renamed to ECMAScript 2015. This edition includes many new features like class, modules, iterators, for/of loop, arrow functions, typed arrays, promises, reflection.

ES6 has following new features included:

  • JavaScript let
  • JavaScript const
  • JavaScript Arrow Functions
  • JavaScript Classes
  • Default parameter values
  • Array.find()
  • Array.findIndex()
  • Exponentiation (**) (ECMAScript 2016)

 

What is difference between JavaScript and es6?

JavaScript is the language. ES (ECMAScript) is the standard governing JavaScript. ES6 is the version of ECMAScript draft in which a lot of features were introduced (classes, arrow functions etc). … JavaScript is an language whereas ES6 is an ECMAScript’s 6th edition. (Answer From Quora)

What are the new features of ES6?

ES6 comes with many new and prompt features like:

  • Immutable variables or constants are now supported
  • Arrow Function
  • Parameter Handling Extended
  • Modules and Classes
  • Extended Object Properties
  • Internationalisation and Localisation

What is Arrow function?

Arrow functions support expressions bodies and statement bodies which returns the value of an expression and makes the syntax more expressive. Arrow functions have lexical ‘this’ feature as well. Arrow (=>) is used as part of the syntax. Lexical this is declared or defined where the function is written. It comes under the umbrella of lexical scope; lexical scope has access to variables that are in its parent scope.

Ex:

//Implementation With Classical Funnction
function add(a,b){
return a+b;
}

//Implementation With Arrow Funnction
const add = (a,b) => a+b;

Differences amongst classes, modules, and proxies?

Proxies enables object creation with a wide variety of behaviours available to host objects. It can be used for logging, profiling, etc.

Module defines the patterns from popular JavaScript module loaders. It supports exporting or importing the values from or to modules without the global namespace. It supports marking the value as the default exported value and max-min values.

Classes are based on the Object Oriented Programming style that is object-oriented programming. The class declaration makes the patterns easier to use. It supports inheritance, base class access, static methods, and constructors.

List data types supported by ES6?

JavaScript supports : Number, Boolean, String, null, undefined, Symbol and Object.

What are the Differences Between ES6 vs ES5?

ES6 : there are two new ways to define variables that are let and const.
ES5 : we could only define the variables by using the var keyword.

ES5 : both function and return keywords are used to define a function.
ES6 : An arrow function is a new feature introduced in ES6 by which we don’t require the function keyword to define the function.

ES5 : It supports primitive data types that are string, number, boolean, null, and undefined.
ES6 : There are some additions to JavaScript data types. It introduced a new primitive data type ‘symbol’ for supporting unique values.

How to Define a Constant in ES6?

In ES6, a constant is defined by a const keyword. ES6 provides a const keyword, which a constant uses and declare a const.

What is Webpack?

Webpack allows you to run an environment that hosts babel. Webpack is opensource JavaScript module bundler that takes modules with dependencies and generates static assets representing those modules.

What are the main benefits of Web pack in ES6?

Benefits of Web pack in ES6:

  • It has included dev server.
  • You only require including one JS tag sharp to server like localhost:8080/assets/bundle.js and get live system updating and advantage management in no costs.
  • Multiple modules and packs are bundled into a solo .js file.

What is Set?

Set are objects and collections of unique values. Duplicate values are ignored, as the collection must have all unique values. The values can be primitive types or object references.
NOTE : NaN and undefined can also be stored in a Set. NaN is considered the same as NaN (even though NaN !== NaN).

What is Spread Operator in ES6?

Spread Operator provides a new way to manipulate array and objects in Es6.A Spread operator is represented by … followed by the variable name.
Example :

let a =[7,8,9];
let b=[1,2,3,...a,10];
console.log(b); // [1,2,3,7,8,9,10]

So spread operator spreads the contents of variable a and concatenates it in b.

Another Example

function print(...z){
console.log(z); 
}

print(1,2,3,4);//[1,2,3,4]

 

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