JavaScript & AJAX interview questions

1. Why so JavaScript and Java have similar name?

A. JavaScript is a stripped-down version of Java

B. JavaScript's syntax is loosely based on Java's

C. They both originated on the island of Java

D. None of the above

2. When a user views a page containing a JavaScript program, which machine actually executes the script?

A. The User's machine running a Web browser

B. The Web server

C. A central machine deep within Netscape's corporate offices

D. None of the above

3. ______ JavaScript is also called client-side JavaScript.

A. Microsoft

B. Navigator

C. LiveWire

D. Native

4. __________ JavaScript is also called server-side JavaScript.

A. Microsoft

B. Navigator

C. LiveWire

D. Native

5. What are variables used for in JavaScript Programs?

A. Storing numbers, dates, or other values

B. Varying randomly

C. Causing high-school algebra flashbacks

D. None of the above

6. _____ JavaScript statements embedded in an HTML page can respond to user events such as mouse-clicks, form input, and page navigation.

A. Client-side

B. Server-side

C. Local

D. Native

7. What should appear at the very end of your JavaScript?

The

B. The

D.

16. Inside which HTML element do we put the JavaScript?

A.

B.

C.

D.

17. What is the correct syntax for referring to an external script called " abc.js"?

A.

B.

C.

D. None of the above

18. Which types of image maps can be used with JavaScript?

A. Server-side image maps

B. Client-side image maps

C. Server-side image maps and Client-side image maps

D. None of the above

19. Which of the following navigator object properties is the same in both Netscape and IE?

A. navigator.appCodeName

B. navigator.appName

C. navigator.appVersion

D. None of the above

20. Which is the correct way to write a JavaScript array?

A. var txt = new Array(1:"tim",2:"kim",3:"jim")

B. var txt = new Array:1=("tim")2=("kim")3=("jim")

C. var txt = new Array("tim","kim","jim")

D. var txt = new Array="tim","kim","jim"

1. 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.
2. What are JavaScript types? - Number, String, Boolean, Function, Object, Null, Undefined.
3. 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);
4. What does isNaN function do? - Return true if the argument is not a number.
5. What is negative infinity? - It’s a number in JavaScript, derived by dividing negative number by zero.
6. What boolean operators does JavaScript support? - &&, || and !
7. What does "1"+2+4 evaluate to? - Since 1 is a string, everything is a string, so the result is 124.
8. How about 2+5+"8"? - Since 2 and 5 are integers, this is number arithmetic, since 8 is a string, it’s concatenation, so 78 is the result.
9. What looping structures are there in JavaScript? - for, while, do-while loops, but no foreach.
10. How do you create a new object in JavaScript? - var obj = new Object(); or var obj = {};
11. How do you assign object properties? - obj["age"] = 17 or obj.age = 17.
12. What’s a way to append a value to an array? - arr[arr.length] = value;
13. What is this keyword? - It refers to the current object.