Here are some of the javascript questions asked in interviews.
What is JavaScript?
Javascript is a scripting language that adds functionality to a web page for example javascript adds animations on clicking a button. JavaScript is also an Object-based Programming language.
State the difference between javascript and java
| Java | JavaScript |
|---|---|
| It is Object-Oriented Programming language | It is an Object-based Scripting language |
| Java applications can run in any virtual machine(JVM) or browser | JavaScript code used to run only in the browser, but now it can run on the server via Node.js |
| Supports multithreading | Does not support multithreading |
What are Javascript datatypes?
Following are the JavaScript Data types:
- Number
- String
- Boolean
- Arrays
- Object
- Undefined
- Null
What is the use of the isNaN function?
This function returns true when the argument passed is not a number.
Between JavaScript and an ASP script, which is faster?
Javascript is a client-side language and does not require assistance from the web. On the other hand, ASP is a server side language and hence is slower than JavaScript. (For details on ASP check the doccumentation.)
What is Negative Infinity?
A number in JavaScript which is derived by dividing a negative number by zero is called Negative Infinity.
Is it possible to break JavaScript Code into several lines?
In a string statement, a backslash can be given at the end of the 1st line to move the rest in the next line.
doccument.write('First line. \Second line.')
And if you change to a new line when not within a string statement, then javaScript ignores the break in the line.
const number =
40
Which company developed JavaScript?
Netscape is a software company that developed JavaScript.
What are undefined and undeclared variables?
Undefined occurs when a variable has been declared but no value is assigned to it. Undefined is not a keyword.
Undeclared occurs when we try to access a variable that is not defined using the const, var or let keyword.
let undefinedVariable
console.log(undefinedVariable) // undefined
console.log(undeclaredVariable) // ReferenceError: undeclaredVariable is not defined
Write the code for adding new elements dynamically?
<!DOCTYPE html>
<html lang="en">
<head>
<title>Dynamic elements</title>
<script type="text/javascript">
function addNode() {
var newP = document.createElement("p");
var textNode = document.createTextNode(" This is a new text node");
newP.appendChild(textNode);
document.getElementById("oldP").appendChild(newP);
}
</script>
</head>
<body>
<p id="oldP">firstP<p>
</body>
</html>
Top comments (2)
Don't work in a place that asks "Which company developed JavaScript" 😅
One more: what is the result of "0.1 + 0.2"?
0.1 + 0.2 is not equal to 0.3. It is not a problem of the language but it is because of the system. Other languages rounds the number, but JavaScript doesn't.