Basic JavaScript Interview Preparation Guide
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JavaScript Tutorial with interview questions and answers. And thousands of JavaScript real Examples.

110 JavaScript Questions and Answers:

1 :: 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 is a platform-independent, event-driven, interpreted client-side scripting and programming language developed by Netscape Communications Corp. and Sun Microsystems.
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2 :: What’s relationship between JavaScript and ECMAScript?

ECMAScript is yet another name for JavaScript (other names include LiveScript). The current JavaScript that you see supported in browsers is ECMAScript revision 3.
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3 :: How do you submit a form using JavaScript?

Use document.forms[0].submit()

(0 refers to the index of the form – if we have more than one form in a page, then the first one has the index 0, second has index 1 and so on).
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4 :: How to read and write a file using JavaScript?

I/O operations like reading or writing a file is not possible with client-side JavaScript. However , this can be done by coding a Java applet that reads files for the script
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5 :: How to detect the operating system on the client machine?

In order to detect the operating system on the client machine, the navigator.appVersion string (property) should be used.
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6 :: What are JavaScript Data Types?

JavaScript Data Types are Number, String, Boolean, Function, Object, Null, Undefined
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7 :: How do you convert numbers between different bases in JavaScript?

Use the parseInt() function, that takes a string as the first parameter, and the base as a second parameter. So to convert hexadecimal 3F to decimal, use parseInt (" 3F" , 16)
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8 :: How to create arrays in JavaScript?

We can declare an array like this
var scripts = new Array()
We can add elements to this array like this

scripts[0] = " PHP"
scripts[1] = " ASP"
scripts[2] = " JavaScript"
scripts[3] = " HTML"

Now our array scripts have 4 elements inside it and we can print or access them by using their index number. Note that index number starts from 0. To get the third element of the array we have to use the index number 2. Here is the way to get the third element of an array.
document.write(scripts[2])
We also can create an array like this
var no_array = new Array(21, 22, 23, 24, 25)
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9 :: How do you target a specific frame from a hyperlink in JavaScript?

Include the name of the frame in the target attribute of the hyperlink in JavaScript. < a href=”http://www.globalguideline.com” target=”myframe”> Global Guide Line< /a>
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10 :: What are a fixed-width table and its advantages in JavaScript?

Fixed width tables are rendered by the browser based on the widths of the columns in the first row, in JavaScript resulting in a faster display in case of large tables. Use the CSS style table-layout:fixed to specify a fixed width table.
If the table is not specified to be of fixed width in JavaScript, the browser has to wait till all data is downloaded and then infer the best width for each of the columns. This process can be very slow for large tables.
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