JavaScript Interview Questions

Java Script:

what is the differene between java and java script...?

Java Script is object based language it is used for front end validations
java is object oriented language object oriented language supports OOP's Object based not suppoted inheritence.

What are JavaScript types?

Number, String, Boolean, Function, Object, Null, Undefined.

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);

What does isNaN function do ?

Return true if the argument is not a number.

What is negative infinity?

It’s a number in JavaScript, derived by dividing negative number by zero.

What boolean operators does JavaScript support?

&&, || and !

What does "1"+2+4 evaluate to?

Since 1 is a string, everything is a string, so the result is 124.

What looping structures are there in JavaScript?

for, while, do-while loops, but no foreach.

How do you create a new object in JavaScript?

var obj = new Object(); or var obj = {};

How do you assign object properties?

obj["age"] = 17 or obj.age = 17

What’s a way to append a value to an array?

arr[arr.length] = value;

What is this keyword?

It refers to the current object.

What is the main difference between Client side JavaScript and and Server side Java Script. How actually they run on both side with Example?

Clientside Javascript encompasses the core language plus extras such as the predefined objects, only relevant to running Javasript in a browser.The clientside javascript is embedded directly in the HTML pages and is interpreted by the browser completly at the run time. Serverside javascript also encompasses the core language plus extas as the predefined objects and functions only relevant to running Javasript in a server.The serverside javascripts are compiled before they are deployed.