Introduction to ES6 Interview Questions and Answers

If you are looking for a job related to ES6, you need to prepare for the 2020 ES6 Interview Questions. Every interview is different from the different job profiles, but still, to clear the interview, you need to have a good and clear knowledge of ES6 processes. Here, we have prepared the important ES6 Interview Question and answers that will help you succeed in your interview.

ES6 is referred to as ECMAScript with version 6 was released in the year 2015. ECMAScript is defined as the scripting language that has been standardized by ECMAScript international. ECMAScript is the proper name of the language that is mainly referred to as JavaScript. It has been mainly used as the client-side server scripting language. It has been released with a lot of features that make the language more flexible and extensive. ES6 is still not having all the browser support.

These questions are divided into two parts are as follows:

Part 1 – ES6 Interview Questions (Basic)

This first part covers basic ES6 Interview Questions and Answers.

Q1. Define ES6 and mention the new features of ES6?

Answer:
Refer to the introduction part for the definition of ES6. Below are the new features listed:

Constants (Immutable variables)
Scoping
Arrow functions
Extended parameter handling
Template literals
Extended literals
Modules
Classes
Enhanced Regular expressions
Enhanced object properties.
Destructuring Assignment
Symbol Type
Iterators
Generator
Map/Set & WeakMap/WeakSet
Typed Arrays
Built-in Methods
Promises
Metaprogramming
Internationalization and Localization.

Q2. How do you use ES6, or the best way to use ES6 in a project?

Answer:
As mentioned, all the browsers do not support ES6, so to use the ES6 script, we need to convert it into the ES5 script, which is supported by all the browsers. To convert into a pre-ES6 script, we required transpilers like Babel. Babel is a popular javascript transpiler used for this purpose, allowing ES-6 code to convert into an ES-5 script to support all the browsers.

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Let us move to the next ES6 Interview Questions.

Q3. What are Constants in ES6?

Answer:
Constants are also referred to as Immutable variables. It means that the value of a constant variable cannot be changed. The value that has been assigned at the time of the declaration remains unchanged. E.g. const X= 5.0, here the value of X remains 5 every time, and it cannot be changed.

Q4. What are Block Scoped variables and functions?

Answer:
This is the common ES6 Interview Question that is asked in an interview. The variables and functions are defined as indefinite blocks. It means these can be used where the variables and functions are defined or declared. If we have declared variable and function in any function block, their scope will be limited to that function only; they cannot be accessible outside the block/function. ‘Const’ keyword cannot change the value of a variable. ‘let’ keyword allows variable value to be re-assigned; it can be in for loop or arrays.

Q5. Explain briefly about Arrow functions?

Answer:
Arrow functions support expressions bodies and statement bodies which returns the expression’s value 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.

Part 2 – ES6 Interview Questions (Advanced)

Let us now have a look at the advanced ES6 Interview Questions and Answers.

Q6. Explain about Webpack and the benefits of using Webpack?

Answer:
Webpack is used to bundle javascript files that can be used in a browser. Webpack processes the application and builds a dependency graph to map each module of the project requirement and generated the bundles. It allows you to run that environment that has been hosted babel. The advantage of using a web pack is that it bundles multiple modules and packs into a single JavaScript file. It integrated the dev server, which helps in updating code and asset management.

Q7. Explain about Default parameter values, Rest parameter, Spread operator?

Answer:
Default parameter values are used to initialize the functions with default values. The value of a parameter can be anything like a null value, number or function.
The rest parameter is used to retrieve all the arguments to invoke the function. It means we can push the items of different categories separately. The rest parameter uses the rest parameter to combine parameters into a single array parameter.
A spread operator is donated by …, and then the variable name has been provided. E.g. ‘…X’ syntax of spread operator. It has been used to manipulate objects and array in ES6 and to copy the enumerable properties from one object to another.

Let us move to the next ES6 Interview Questions.

Q8. Explain about Internationalization and localization?

Answer:
These are the APIs that are standard API of JavaScript that helps in different tasks like collation, Number formatting, Currency formatting, Date and time formatting.

Collation: It is used for searching within a set of strings and sorting a set of strings. It is parameterized by locale and aware of Unicode.
Number Formatting: Numbers can be formatted with localized separators and digit grouping. The other things that include are style formatting, numbering system, percent, and precision.
Currency formatting: Numbers can be formatted mainly with currency symbols, with localized separators and digit grouping.
Date and time formatting: it has been formatted with localized separators and ordering. The format can be short, long and other parameters like locale and time zone.

Q9. What is a Destructuring assignment, and explain in brief?

Answer:
This is the frequently asked ES6 Interview Questions which is asked in an interview. Destructuring assignment is used to bind the set of a variable to the corresponding values. It mainly refers to the use of patterns to extract the parts of an object. A destructuring assignment has different forms like array matching, object matching, shorthand notation, object matching, deep matching, object and array matching, default values, parameter context matching, and fail-soft destruct. Some are explained as:

Array matching/object matching, shorthand notation/ object matching, deep matching: It is intuitive and flexible of arrays into individual variables during an assignment.
Object and Array matching: It is simple and defined default values for destructuring of objects and arrays.

Q10. Explain briefly about classes, modules, and proxies?

Answer:
Classes are based on the OOP 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.

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