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1.	What are constants?
Answer» <html><body><p>You can <a href="https://interviewquestions.tuteehub.com/tag/call-412416" style="font-weight:bold;" target="_blank" title="Click to know more about CALL">CALL</a> the immutable variables as constants. The value of a constant once defined remains the same and we cannot change it. This is the value that you introduce during the declaration. For <a href="https://interviewquestions.tuteehub.com/tag/example-239971" style="font-weight:bold;" target="_blank" title="Click to know more about EXAMPLE">EXAMPLE</a>, const Y= 6.0. This value of Y would continue to be 6 <a href="https://interviewquestions.tuteehub.com/tag/throughout-7258007" style="font-weight:bold;" target="_blank" title="Click to know more about THROUGHOUT">THROUGHOUT</a> and it won’t be <a href="https://interviewquestions.tuteehub.com/tag/changed-913862" style="font-weight:bold;" target="_blank" title="Click to know more about CHANGED">CHANGED</a>.</p></body></html>

2.	What are the classes and proxies?
Answer» <html><body><p><strong>Class</strong>- You can use the patterns easily with OOP based class declaration. It <a href="https://interviewquestions.tuteehub.com/tag/works-17618" style="font-weight:bold;" target="_blank" title="Click to know more about WORKS">WORKS</a> <a href="https://interviewquestions.tuteehub.com/tag/readilybr-2976648" style="font-weight:bold;" target="_blank" title="Click to know more about READILY">READILY</a> with constructors, supports <a href="https://interviewquestions.tuteehub.com/tag/base-239221" style="font-weight:bold;" target="_blank" title="Click to know more about BASE">BASE</a> class <a href="https://interviewquestions.tuteehub.com/tag/access-846773" style="font-weight:bold;" target="_blank" title="Click to know more about ACCESS">ACCESS</a>, inheritance and static methods. OOP refers to Object-Oriented Programming.</p><p><strong>Proxies</strong>- With proxies, you get to create <a href="https://interviewquestions.tuteehub.com/tag/objects-20533" style="font-weight:bold;" target="_blank" title="Click to know more about OBJECTS">OBJECTS</a> and you can host the objects with a huge behavior diversity. Proxies can help in profiling and logging as well.</p></body></html>

3.	What is the advantage of using Webpack?
Answer» <html><body><p>The <a href="https://interviewquestions.tuteehub.com/tag/advantage-368337" style="font-weight:bold;" target="_blank" title="Click to know more about ADVANTAGE">ADVANTAGE</a> of a web pack is explained through its description above. It helps in making a <a href="https://interviewquestions.tuteehub.com/tag/bundle-905567" style="font-weight:bold;" target="_blank" title="Click to know more about BUNDLE">BUNDLE</a> of the project modules into a single <a href="https://interviewquestions.tuteehub.com/tag/javascript-6831" style="font-weight:bold;" target="_blank" title="Click to know more about JAVASCRIPT">JAVASCRIPT</a> <a href="https://interviewquestions.tuteehub.com/tag/file-11330" style="font-weight:bold;" target="_blank" title="Click to know more about FILE">FILE</a>. Webpack <a href="https://interviewquestions.tuteehub.com/tag/combined-409631" style="font-weight:bold;" target="_blank" title="Click to know more about COMBINED">COMBINED</a> the Dev server which helps in updating the code and asset management.</p></body></html>

4.	What is spread, default and rest parameter?
Answer» <html><body><p><strong>Spread Operator</strong>- Donated by ‘...’ and is followed by the variable. The syntax of the spread operator would look like this for example:- ‘...X’. Spread operators manipulated objects and arrays which is the prime reason it is used in ES6. It is used for copying the property of one object to another.</p><p><strong>Default Operator</strong>- In order to initialize a function using default values, the default operator is deployed. The parameter’s <a href="https://interviewquestions.tuteehub.com/tag/value-238057" style="font-weight:bold;" target="_blank" title="Click to know more about VALUE">VALUE</a> can be anything- a number or a function or null.</p><p><strong>Rest Parameter</strong>- This operator is used for recovering all the arguments that are required to invoke a function. This allows <a href="https://interviewquestions.tuteehub.com/tag/us-243201" style="font-weight:bold;" target="_blank" title="Click to know more about US">US</a> to put items belonging to different <a href="https://interviewquestions.tuteehub.com/tag/categories-249167" style="font-weight:bold;" target="_blank" title="Click to know more about CATEGORIES">CATEGORIES</a> separate. The rest parameter allows combining the parameters in a common array parameter.</p> 12. What is Webpack ? <p>Webpack allows you to create a pile of the javascript files that are usable in the browser. With Webpack, we can <a href="https://interviewquestions.tuteehub.com/tag/build-403683" style="font-weight:bold;" target="_blank" title="Click to know more about BUILD">BUILD</a> the dependency graph, do application processing. With the dependency graph, one can map every module of the project. This helps in matching up with project requirements.</p></body></html>

5.	Define Temporal Dead Zone in ES6.
Answer» <html><body><p>The temporal dead zone can be <a href="https://interviewquestions.tuteehub.com/tag/defined-947013" style="font-weight:bold;" target="_blank" title="Click to know more about DEFINED">DEFINED</a> as the time span which exists between the time taken for binding of a variable and its declaration in a program. The temporal dead zone exists so that program errors can be easily <a href="https://interviewquestions.tuteehub.com/tag/identified-1036116" style="font-weight:bold;" target="_blank" title="Click to know more about IDENTIFIED">IDENTIFIED</a> as a variable that can be <a href="https://interviewquestions.tuteehub.com/tag/made-1082584" style="font-weight:bold;" target="_blank" title="Click to know more about MADE">MADE</a> <a href="https://interviewquestions.tuteehub.com/tag/accessible-366579" style="font-weight:bold;" target="_blank" title="Click to know more about ACCESSIBLE">ACCESSIBLE</a> before its declaration. Also for making const work properly, the temporal dead zone can be used. It is also used to proof guard JavaScript which is basically a <a href="https://interviewquestions.tuteehub.com/tag/mechanism-15329" style="font-weight:bold;" target="_blank" title="Click to know more about MECHANISM">MECHANISM</a> used for runtime.</p></body></html>

6.	What is a generator in JavaScript?
Answer» <html><body><p>With the <a href="https://interviewquestions.tuteehub.com/tag/launch-246614" style="font-weight:bold;" target="_blank" title="Click to know more about LAUNCH">LAUNCH</a> of ES6, a new way of working with functions and iterators came into work. These are called generators. A generator is nothing but a function that can <a href="https://interviewquestions.tuteehub.com/tag/stop-1228105" style="font-weight:bold;" target="_blank" title="Click to know more about STOP">STOP</a> at the point of time when the user commands it to do so and then continue working just from the point where it stopped. In other words, a generator has <a href="https://interviewquestions.tuteehub.com/tag/properties-11511" style="font-weight:bold;" target="_blank" title="Click to know more about PROPERTIES">PROPERTIES</a> of a function but also works as an iterator. It does not work like other lines of code which need to be completed for execution.</p><p>Generators work on a run-to-completion model which makes it easier for the developers to compile a <a href="https://interviewquestions.tuteehub.com/tag/program-246414" style="font-weight:bold;" target="_blank" title="Click to know more about PROGRAM">PROGRAM</a>. Generators can also be defined as a special class of functions that work to simplify the task of coding iterators in a program. It produces a sequence of results rather than producing a single value. It enables the developer to generate a series of values at a time.</p><p><em>This is very important<strong> javascript ES6 Interview </strong><strong>Questions</strong>.</em></p></body></html>

7.	Explain the reason for using ES6 classes.
Answer» <html><body><p>ES6 classes have been found to be very useful to the developers. Some of the major uses of ES6 classes are as <a href="https://interviewquestions.tuteehub.com/tag/follows-457929" style="font-weight:bold;" target="_blank" title="Click to know more about FOLLOWS">FOLLOWS</a>:</p><ul><li>ES6 classes have a simpler and less error-prone syntax.</li><li>As far as setting up inheritance hierarchies are concerned, ES6 is considered as the best option as it uses new syntax with the old syntax which minimizes the <a href="https://interviewquestions.tuteehub.com/tag/errors-15514" style="font-weight:bold;" target="_blank" title="Click to know more about ERRORS">ERRORS</a> and eases the process.</li><li>ES6 classes help in defending the developers from <a href="https://interviewquestions.tuteehub.com/tag/failing-2080752" style="font-weight:bold;" target="_blank" title="Click to know more about FAILING">FAILING</a> to use new ones <a href="https://interviewquestions.tuteehub.com/tag/properly-1733030" style="font-weight:bold;" target="_blank" title="Click to know more about PROPERLY">PROPERLY</a> with the constructor function. This is one of the most common errors that occur with the developers during the use of a new operator. Classes remove this error by having the constructor throw an exception if this proves to be an invalid object for the constructor.</li><li>Classes also help to call the method which is of the prototype’s version. This version is <a href="https://interviewquestions.tuteehub.com/tag/much-249971" style="font-weight:bold;" target="_blank" title="Click to know more about MUCH">MUCH</a> simpler with the new ES6 syntax than the old versions.</li></ul></body></html>

8.	Differentiate between .call and .apply.
Answer» <html><body><table><tbody><tr><th>.call</th><th>.apply</th></tr></tbody><tbody><tr><td>.call is used to invoke the functions, and the first <a href="https://interviewquestions.tuteehub.com/tag/parameter-244658" style="font-weight:bold;" target="_blank" title="Click to know more about PARAMETER">PARAMETER</a> will become the value of this within the function created by the developer.</td><td>.apply is also used to invoke the functions but it takes an array of arguments. This array works as the next <a href="https://interviewquestions.tuteehub.com/tag/argument-239210" style="font-weight:bold;" target="_blank" title="Click to know more about ARGUMENT">ARGUMENT</a> and the function works this way.</td></tr><tr><td>.call is used to call the method which takes the owner object as its argument.</td><td>.apply method is used to write methods. These methods can be used on several objects.</td></tr><tr><td>It accepts two parameters namely objectInstance and arguments</td><td>It accepts two parameters namely objectInstance and arrayofArguments</td></tr><tr><td>.call takes several arguments <a href="https://interviewquestions.tuteehub.com/tag/separated-2256042" style="font-weight:bold;" target="_blank" title="Click to know more about SEPARATED">SEPARATED</a> by <a href="https://interviewquestions.tuteehub.com/tag/commas-923101" style="font-weight:bold;" target="_blank" title="Click to know more about COMMAS">COMMAS</a>.</td><td>.apply takes several arguments with the <a href="https://interviewquestions.tuteehub.com/tag/help-239643" style="font-weight:bold;" target="_blank" title="Click to know more about HELP">HELP</a> of an array of arguments.</td></tr></tbody></table></body></html>

9.	Differentiate between ES6 class and ES5 function constructors.
Answer» <html><body><table><tbody><tr><th>ES6 class</th><th>ES5 Function Constructors</th></tr></tbody><tbody><tr><td>ES6 class basically does the work of <a href="https://interviewquestions.tuteehub.com/tag/defining-2052307" style="font-weight:bold;" target="_blank" title="Click to know more about DEFINING">DEFINING</a> a new <a href="https://interviewquestions.tuteehub.com/tag/object-11416" style="font-weight:bold;" target="_blank" title="Click to know more about OBJECT">OBJECT</a> and appending functions to its prototype.</td><td>ES5 Function constructors work and look the same but the main difference is observed when the <a href="https://interviewquestions.tuteehub.com/tag/developer-25513" style="font-weight:bold;" target="_blank" title="Click to know more about DEVELOPER">DEVELOPER</a> uses the Inheritance property.</td></tr><tr><td>They can be considered as the syntax base for constructor functions.</td><td>These can only be <a href="https://interviewquestions.tuteehub.com/tag/executed-979171" style="font-weight:bold;" target="_blank" title="Click to know more about EXECUTED">EXECUTED</a> with the help of a new operator.</td></tr><tr><td>ES6 class allows the developers to instantiate objects using the new operator.</td><td>ES5 function constructors <a href="https://interviewquestions.tuteehub.com/tag/focus-25840" style="font-weight:bold;" target="_blank" title="Click to know more about FOCUS">FOCUS</a> on how the objects are instantiated.</td></tr><tr><td>They also ensure the developer that this keyword which is basically used inside the class only refers to the object that is being created by the developer.</td><td>ES5 function constructor focus on implementing the reusable object creation code. Any function can be used as a constructor.</td></tr></tbody></table></body></html>

10.	Explain the benefits of using spread syntax in ES6. How is it different from the rest of the syntax?
Answer» <html><body><p>As far as coding in a functional paradigm is concerned, using the spread syntax in ES6 can prove to be heavily beneficial. The spread syntax can be easily used to create copies of <a href="https://interviewquestions.tuteehub.com/tag/arrays-11294" style="font-weight:bold;" target="_blank" title="Click to know more about ARRAYS">ARRAYS</a> or objects. Using spread syntax in a program does not need to resort to Object.create, slice or any library function. The spread syntax is widely used in Redux and rx.js projects.</p><p>While on the other hand, the rest syntax feature of ES6 is used to pass an arbitrary number of arguments to a function. It can also be considered as a <a href="https://interviewquestions.tuteehub.com/tag/shorthand-1206362" style="font-weight:bold;" target="_blank" title="Click to know more about SHORTHAND">SHORTHAND</a> in JavaScript programming. Rest syntax can be considered as the opposite of spread syntax. It takes <a href="https://interviewquestions.tuteehub.com/tag/data-25577" style="font-weight:bold;" target="_blank" title="Click to know more about DATA">DATA</a> and stuffs it into an array instead of unpacking the data. In addition to that, it works suitably in function arguments, arrays as well as to object destructuring assignments.</p><p><em><strong>Note</strong>: This </em><em>question</em><em> is asked in almost all <strong>ES6 Interview Questions</strong>.</em></p></body></html>

11.	Explain the motivation behind Symbols to ES6.
Answer» <html><body><p>Symbols are a particular kind of object, newly added in the sixth version of ECMAScript which can be used as a unique property name in the objects. Using Symbol in the place of String (as it was done in the previous versions) allows the programmer to use different modules that can create properties that will not be problematic to each other. Another <a href="https://interviewquestions.tuteehub.com/tag/huge-1032540" style="font-weight:bold;" target="_blank" title="Click to know more about HUGE">HUGE</a> benefit of Symbols is that they can be made private and the properties defined cannot be accessed by any <a href="https://interviewquestions.tuteehub.com/tag/user-25565" style="font-weight:bold;" target="_blank" title="Click to know more about USER">USER</a> or <a href="https://interviewquestions.tuteehub.com/tag/developer-25513" style="font-weight:bold;" target="_blank" title="Click to know more about DEVELOPER">DEVELOPER</a> who does not have direct <a href="https://interviewquestions.tuteehub.com/tag/access-846773" style="font-weight:bold;" target="_blank" title="Click to know more about ACCESS">ACCESS</a> to the Symbol. They <a href="https://interviewquestions.tuteehub.com/tag/comprise-927303" style="font-weight:bold;" target="_blank" title="Click to know more about COMPRISE">COMPRISE</a> of a function that can be used to create different symbols that can work differently. But they do not have any literal syntax, unlike the other primitives of JavaScript.</p></body></html>

12.	Why are arrow functions used in ES6?
Answer» <html><body><p>Arrow functions are <a href="https://interviewquestions.tuteehub.com/tag/one-241053" style="font-weight:bold;" target="_blank" title="Click to know more about ONE">ONE</a> of the major reasons for the popularity of ES6 due to the reasons mentioned below:</p><ul><li><strong>Safety of scope</strong>: Consistent use of arrow functions guarantee to use the same thisObject as the root. Using the arrow functions provides scope safety because even if a single standard function <a href="https://interviewquestions.tuteehub.com/tag/callback-412427" style="font-weight:bold;" target="_blank" title="Click to know more about CALLBACK">CALLBACK</a> is mixed with some arrow functions, the probability of scope getting disturb increases.</li><li><strong>Compactness</strong>: It is easier to read and write when it comes to arrow functions as compared to other functions. This provides a less <a href="https://interviewquestions.tuteehub.com/tag/complex-926309" style="font-weight:bold;" target="_blank" title="Click to know more about COMPLEX">COMPLEX</a> approach of using ES6 as well as the arrow functions.</li><li><strong>Provides clarity</strong>: A developer can easily identify what “ thisObject” is and find out the next-higher function statement after the arrow function statement if he/she uses arrow function in most of the <a href="https://interviewquestions.tuteehub.com/tag/program-246414" style="font-weight:bold;" target="_blank" title="Click to know more about PROGRAM">PROGRAM</a>. It will provide <a href="https://interviewquestions.tuteehub.com/tag/huge-1032540" style="font-weight:bold;" target="_blank" title="Click to know more about HUGE">HUGE</a> clarity and easy detection of errors in any program.</li></ul></body></html>

13.	What do you mean by IIFEs?
Answer» <html><body><p>IIFEs or Immediately Invoked <a href="https://interviewquestions.tuteehub.com/tag/function-11303" style="font-weight:bold;" target="_blank" title="Click to know more about FUNCTION">FUNCTION</a> Expressions are the expressions which are immediately executed as soon as it is created. IIFEs are <a href="https://interviewquestions.tuteehub.com/tag/used-763273" style="font-weight:bold;" target="_blank" title="Click to know more about USED">USED</a> to avoid the excessive use of <a href="https://interviewquestions.tuteehub.com/tag/global-473628" style="font-weight:bold;" target="_blank" title="Click to know more about GLOBAL">GLOBAL</a> <a href="https://interviewquestions.tuteehub.com/tag/namespace-246982" style="font-weight:bold;" target="_blank" title="Click to know more about NAMESPACE">NAMESPACE</a> because all the variables which are used inside the IIFE cannot be viewed outside its scope. In other words, IIFEs are design patterns also known as Self Executing Anonymous Functions because it executes on its own.</p></body></html>

14.	Explain the difference between ES5 and ES6?
Answer» <html><body><table><tbody><tr><th>ES5</th><th>ES6</th></tr></tbody><tbody><tr><td>ES5 is the 5th edition of ECMAScript which was <a href="https://interviewquestions.tuteehub.com/tag/standardized-1224469" style="font-weight:bold;" target="_blank" title="Click to know more about STANDARDIZED">STANDARDIZED</a> in 2009. This version has been successfully implemented in all web browsers.</td><td>ES6 is the <a href="https://interviewquestions.tuteehub.com/tag/6th-332122" style="font-weight:bold;" target="_blank" title="Click to know more about 6TH">6TH</a> edition of ECMAScript which was standardized in <a href="https://interviewquestions.tuteehub.com/tag/2015-291056" style="font-weight:bold;" target="_blank" title="Click to know more about 2015">2015</a>. This version has been partially implemented in most web browsers.</td></tr><tr><td>The function keyword is <a href="https://interviewquestions.tuteehub.com/tag/mandatory-553804" style="font-weight:bold;" target="_blank" title="Click to know more about MANDATORY">MANDATORY</a> to use to define the functions.</td><td>In this, to define the function, the function keyword is not needed.</td></tr><tr><td>The return keyword is also mandatory to use to define the functions</td><td>The return keyword is not needed to define the functions.</td></tr><tr><td>ES5 has lower performance due to the absence of a few features.</td><td>ES6 has a <a href="https://interviewquestions.tuteehub.com/tag/comparatively-925352" style="font-weight:bold;" target="_blank" title="Click to know more about COMPARATIVELY">COMPARATIVELY</a> higher performance.</td></tr></tbody></table></body></html>