17 JavaScript Interview Questions & Answers

17 JavaScript Interview Questions & Answers

The questions you must be prepared to crack JavaScript Interview.

We as a whole know how troublesome it is these days to have a prospective employee meet-up. Along these lines, in the event that we have one, it regards be set up for it as opposed to simply go and be there for the meeting. Being readied will build our shot of cracking the interview and be the chosen possibility for having the employment. It regards know a portion of the JavaScript interview questions with the goal that we are not shocked when those questions are asked by the questioner. The principal goal of a specialized meeting is to judge whether you are the appropriate individual to be a colleague of the organization. There are sure strides that you should take after with the goal that you can break the interview. The above all else thing is to set up some question which can most likely be asked at the meeting. Furthermore, you have to sharpen the diverse nature of coding which you may think could be the one which the meeting may request that you perform. Make questions yourself and fathom those utilizing codes. Before setting off to the meeting leave a hole of a couple of hours from examining so you don’t get over-burden with stuff. It is far and away superior to rest for 60 minutes before the meeting so you confront the meeting with a crisp personality. There are sure viewpoints that you should recall while you are on the hot seat for being chosen. You should be set up for anything, make inquiries to make yourself clear with respect to any uncertainty that you have in regards to the question asked, set aside your opportunity to answer and act naturally amid the meeting. In the event that you take after these means, you are sure to crack the meeting and be the anointed one.

Being here you are at the right place for preparing some of the JavaScript interview questions. Let us have a look at some so that we can easily tackle those if asked.

What do you mean by JavaScript?

This may be the first question that you are asked when you appear for the interview. It is a scripting language which can be used from the client side or the server side and can be inserted into pages of HTML. This is also understood by the web browser. It is a programming language which is object oriented.

After looking at this question you may be thinking that answers to this sort of question are known to you. Definitely, they are known to you as your subject of specialization is JavaScript and this is known to us and also the interviewer. But then also such questions are asked basically for two reasons: one is that it helps the interviewer to know your basic knowledge about the subject and secondly to make you feel homely during the interview. They proceed to ask difficult questions later. We also follow the same pattern and prepare these basic questions so that our memories are refreshed.

Explain the difference between Java and JavaScript?

Java is the complete programming language where JavaScript is a program that is coded and can be included in a page of HTML. They are not dependent on each other and are created for a different purpose. Java is a nature of object-oriented programs like C+ and C++, on the other hand, JavaScript is a scripting language from the client side and it is also known as unstructured programming.

Name the types of JavaScript?

The names of JavaScript types are as follows:

  • Number
  • String
  • Boolean
  • Function
  • Object
  • Null
  • Undefined

What is the use of isNaN function?

It is returned true if the argument that is put forward is not a number otherwise it is false.

Explain with a reason which is faster JavaScript or ASP Script?

JavaScript is faster than ASP Script. The reason for this fastness is that JavaScript is a client sided language and does not require the help of a web server for operation. But ASP Script is a server sides language and requires the help of a web server for functionality.

It is a type of a number in JavaScript which is obtained by dividing a negative number by zero.

Explain the different actions that are performed by means of JavaScript?

There are various functions that are performed by means of JavaScript. The functions are:

  • Implementation of privacy policies can be done more effectively using JavaScript and unauthorized access to files is denied. This makes the computer more secure.
  • It is helpful in setting browser preference and is helpful in receiving a request for the server that is used by the client.
  • The settings used to get saved on the client side in features like action buttons, printing, and appearance.
  • It helps in easily launching an application on the computer of the client by usage of interactive data that is to be communicated between the server and the client.
  • It is helpful in a reading of files that are situated on the client side or the server side.
  • It helps in easily capturing data that is live-streamed between the server and the machine of the client for retransmission.
  • It allows safety and security to the applications from the outside world.

This nature of preparation of JavaScript interview questions will enable you to organize the known answers properly and also to know about certain questions about which you have doubts. The questions sometime may seem very simple but then also it is better to practice so that there is no confusion and you do not fumble while answering.

Explain the separation of JavaScript language from objects?

The creation and treatment of applications are done by JavaScript for scripting so that the browser becomes compatible with usage. The language allows the syntax to change the current environment and so can be separated from the object. The page element of the HTML document is kept by this language. The elements of the page are made to be synced with the objects used in the documents by JavaScript. Creation of objects linked with the page elements or another element in a language is made by JavaScript. The development concept and the sharing of each factor are allowed by the separation. Using the weekly typed language dynamic data can be presented using JavaScript. Any nature of the action required for support of the user interface and the graphics are supported by this language.

Explain the usage of DOM?

Document Object Model is the full form of DOM. It is used for the creation of a model using documents of pages of the web which contains objects like the elements, the link and the like. Manipulation can be done to the objects and certain nature of action can be added, deleted or changed using DOM. It is responsive to API calls which results in a recommendation of DOM in the documented level. Additional behavior can be supported on the web page by usage of DOM. The usage of API gives it an upper hand than other models that exist. Codes used by DOM can be reused for meeting the requirement of the real world so as to make the entire program interoperable.

Explain the importance of <SCRIPT> tag?

  • <SCRIPT> tag is inside which JavaScript is used in HTML document. These tags provide necessary information to the browser like an alert for the program so that is can begin the interpretation of all the text that is between the tags.
  • JavaScript interpreter is used by <SCRIPT> tag for handling the libraries that are printed or the codes that are used in the program.
  • These tags enable the browser to know whether the text that is written between <SCRIPT> and </SCRIPT> tags are recognizable by JavaScript.

Explain why JavaScript is known as the script for all browsers?

So how are you feeling now about the JavaScript interview questions? It is getting into depth and unless they are prepared properly it is difficult to answer those in an organized manner. It was better to be prepared, than to be caught fumbling while answering the questions. The answer to this question is:

JavaScript is composed after <SCRIPT> tag and it is encompassed in the middle of the <!- – your code – > tags, this is otherwise called comment tag. JavaScript translator treats the tag with the end goal that it treats every one of the lines in the remarks as script lines. The JavaScript comment begins with/inside the <SCRIPT> tag. The script is contained inside <HTML> tag that contains a comment tag. The program that is non-perfect with JavaScript overlooks the lines and proceed onward, yet good programs dependably regard it as a script and execute it. The program treats the composed lines between the remark tag as ordinary lines and simply thinking about the remark overlooks it. A few programs simply treat the <!- – comment – > as a comment just and overlooks whatever is composed inside it.

What are the various requirements that web application for using JavaScript?

There are requirements of various things when a user uses JavaScript. The requirements are:

  • Validation of data entry: If this field is filled out then it indicates that during dealing out with the server the side of the client can have interaction with these.
  • Serverless CGIs: It helps in a description of the processes that are not suitable for use with JavaScript and they are programmed as CGI on the server. It is the cause of low performance for the reason of more interaction amongst the application and the user.
  • Dynamic HTML interactivity: Without the use of any other language for scripting this allows the dynamic placement of data.
  • Prototyping of CGI: User interface could be accessed using less time using this before the implementation of GCI application.

Name the objects that are used in JavaScript?

A hierarchical structure of an object is maintained in JavaScript. There are certain objects which show the relationship between objects using this particular language.

  • Window object: In the hierarchy, this is the topmost object. It is the representation of the area of the content of the browser which has the HTML documents. Every frame is a window and has some nature of action inside it.
  • Document object: It is formed by many objects which are of a different nature and it gets loaded into a window. It is the content that is written within the script.
  • Form object: This nature of the object helps the interaction with the user. It is used to represent the form of element inside <FORM> … </FORM>.

These JavaScript interview questions have to be studied meticulously in order to be able to give the proper answer. Do not memorize the answers. Go through the answers and follow the logic that is in place while giving the answer. This will help you to be confident rather than memorizing. Memorizing has another disadvantage. If you forget a certain part of the answer then you in a loss and you will fumble while answering. Let us see some other question which will be of your help to crack this nature of the interview and be the chosen one to have the job.

What is the importance of object naming in JavaScript?

  • This is used for the creation of script references to the objects while names are assigned to various objects which are scriptable in the code of HTML. The browsers which are compatible with the script try to find the optional tags and the attributes which enables assigning names which are unique to every object.
  • Identification and location of the elements are done easily by usage of the names which acts as nametags. The references that are made for the objects are from top to the bottom of the hierarchy.

The importance of object naming is that it provides an easy way of locating the objects and the linkage between them can be done in an easy manner.

Explain the methods used in JavaScript?

A method is instructive that gets performed over an activity that is identified with the object. Method either acts on certain objects or influence any piece of the script or a report. An object is permitted to have any number of methods but they must be associated with the other object.

Dynamic interactions amongst users are performed using this function. The statement that is first is executed to send a form to the server when the button of submitting is pressed. The two statements have relation only with the form.

Explain what you know about document loading?

Loading of the document means that it is getting ready to be executed by the particular system. The loading happens when there is the running of that document on the system. JavaScript is allowed by the application to look at all the various properties that are present in the object and allows inclusion of all the values of properties which are used by the content which is being rendered for the page that is going to be loaded. It is a beneficial practice to embrace the content in <SCRIPT> tags and statements that are in the body section of the document.

Explain the function of Deferred Scripts?
These are scripts the statement of which runs as such that the statement appears to be grouped together as a function. It defines a block which statement of script consists of and helps to run those that are in <SCRIPT> tags which happen after all the various statements are loaded on to the browser. The visibility inside the <SCRIPT> tag can be easily seen by this functionality. Every function over here starts with (), the name of the function is written afterward which also includes the parentheses. After the loading of the function, it is ready to be run when there is a necessity. It is very useful when a function needs to run just after being loaded. Usage of event handlers are made by Window objects which trigger the nature of the response to the action of the user and then the handler is onLoad.

Thus, you can see that there can be endless JavaScript interview questions that can be asked in a meeting. There are some different things additionally that we should set ourselves up while we mean to crack the interview. Right off the bat, we should be in time for the interview. It ought not to be with the end goal that you are late to reach the venue of the interview. You must be dressed legitimately in formals to show up for the interview. You should keep up all the etiquette that should be kept up while you are in the scene. Last however not the minimum you should be certain while noting the inquiries. Set aside your opportunity to comprehend the question and afterward reply. It might so happen that you don’t have the foggiest idea about the response to a specific question it is ideal to admit than to give a wrong answer.

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