JavaScript Interview Questions and Answers
Here you can find JavaScript Interview Questions and Answers.
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In this JavaScript Interview Questions and Answers section you can learn and practice JavaScript Interview Questions and Answers to improve your skills in order to face
technical inerview by IT companies. By Practicing these interview questions, you can easily crack any JavaScript interview.
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You no need to worry, we have given lots of JavaScript Interview Questions and Answers and also we have provided lots of FAQ's to quickly answer the questions in the
JavaScript technical interview.
JavaScript Interview Questions and Answers
What is JavaScript?
JavaScript is a general-purpose programming language designed to let programmers of all skill levels control the behavior of software objects.
The language is used most widely today in Web browsers whose software objects tend to represent a variety of HTML elements in a document and the document itself.
But the language can be--and is--used with other kinds of objects in other environments.
For example, Adobe Acrobat Forms uses JavaScript as its underlying scripting language to glue together objects that are unique to the forms generated by Adobe Acrobat.
Therefore, it is important to distinguish JavaScript, the language, from the objects it can communicate with in any particular environment.
When used for Web documents, the scripts go directly inside the HTML documents and are downloaded to the browser with the rest of the HTML tags and content.
JavaScript Interview Questions and Answers
Is JavaScript case sensitive?
Yes, absolutely. For example, the function getElementById is not the same as the function getElementbyID. Keeping your capitalization consistent is important.
JavaScript is a platform-independent, event-driven, interpreted client-side scripting and programming language developed by Netscape Communications Corp. and Sun
Microsystems.
JavaScript Interview Questions and Answers
Are Java and JavaScript the Same?
No. java and JavaScript are two different languages.
Java is a powerful object - oriented programming language like C++, C whereas JavaScript is a client-side scripting language with some limitations.
JavaScript Interview Questions and Answers
What is ‘this’ keyword in JavaScript?
‘This’ keyword is used to point at the current object in the code. For instance: If the code is presently at an object created by the help of the ‘new’ keyword, then ‘this’
keyword will point to the object being created.
JavaScript Interview Questions and Answers
Explain the different types of pop-up boxes you can create in JavaScript.
There are three main types of pop-up boxes in JavaScript: alert boxes, confirm boxes, and prompt boxes.
•Alert Box: Used to confirm that a user understands a vital piece of information before proceeding. The user must click OK to exit the box.
window.alert("Alert text here."); •Confirm box:a Used when user verification is required. It will return TRUE if the user clicks OK, and FALSE if the user clicks CANCEL.
window.confirm("Confirm text here."); •Prompt box: Used if the user needs to input something before proceeding. When the user inputs a value and presses OK, the prompt
box will return the input value. If the user clicks CANCEL without inputting a value, the input value will return as null.
window.prompt("Prompt box text","Default value");
JavaScript Interview Questions and Answers
What are JavaScript Data Types?
JavaScript Data Types are Number, String, Boolean, Function, Object, Null, Undefined
JavaScript Interview Questions and Answers
What looping structures are there in JavaScript?
JavaScript supports the for loop, while loop, do-while loop, but there is no foreach loop in JavaScript.
JavaScript Interview Questions and Answers
What are the different boolean operators in JavaScript?
•&& – the “and†operator.
•|| – the “or†operator.
•! – the “not†operator.
JavaScript Interview Questions and Answers
How is JavaScript different from Java?
JavaScript was developed by Brendan Eich of Netscape Java was developed at Sun Microsystems. While the two languages share some common syntax, they were
developed independently of each other and for different audiences. Java is a full-fledged programming language tailored for network computing it includes hundreds of its own
objects, including objects for creating user interfaces that appear in Java applets (in Web browsers) or standalone Java applications. In contrast, JavaScript relies on whatever
environment it's operating in for the user interface, such as a Web document's form elements.
JavaScript was initially called LiveScript at Netscape while it was under development. A licensing deal between Netscape and Sun at the last minute let Netscape plug the "Java"
name into the name of its scripting language. Programmers use entirely different tools for Java and JavaScript. It is also not uncommon for a programmer of one language to be
ignorant of the other. The two languages don't rely on each other and are intended for different purposes. In some ways, the "Java" name on JavaScript has confused the world's
understanding of the differences between the two. On the other hand, JavaScript is much easier to learn than Java and can offer a gentle introduction for newcomers who want to
graduate to Java and the kinds of applications you can develop with it.
JavaScript Interview Questions and Answers
What is the difference between == and === ?
The == checks for value equality, but === checks for both type and value.
