Page 228 - Web Applications (803) Class 12
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13. What is NaN? Explain using an example. [CBSE COMPTT 2023]
Ans. NaN, which stands for “Not a Number,” is a special JavaScript value that represents an invalid numeric value. It can
result from a variety of operations, such as dividing by zero, computing the square root of a negative number, or
parsing a string that cannot be transformed to a number.
Example: const ans = 30 / 0;
document.write(result); // will result in NaN
NaN can also be used to check if a value is a number using the isNaN() functionIn JavaScript, NaN is a helpful
value for handling errors and unexpected results.
14. Explain the difference between for and while loops in JavaScript with an example.
Ans.
for loop while loop
The number of iterations is known beforehand. The number of iterations is not known, and the loop
continues as long as a specified condition is true.
The initialization, condition, and iteration statements Only the condition is provided at the beginning of the
are provided at the beginning of the loop. loop, initialization and iteration are handled outside
the loop.
// Print namaste 5 times using a for loop // Print namaste 5 times using a for loop
for (var i = 1; i <= 5; i++) var i = 1;
document.write(“Namaste”); while (i <= 5) {
document.write(“Namaste”);
i++;
}
Computational Thinking
C. Competency-based/Application-based questions:
1. A JavaScript array is initialized as follows:
even=[2,4,6,8,10];
Write the status of the array after each of the following operations:
i. even.shift();
ii. even.pop();
iii. even.push(12);
iv. even.unshift(100);
Ans. i. 4,6,8,10
ii. 4,6,8
iii. 4,6,8,12
iv. 100,4,6,8,12
2. Rachna has created an external JavaScript file named “ext_code.js” to include in her webpage. Write code to link
the above file in the webpage’s HTML code. Also, mention where the code should be placed in the HTML code.
Ans. To include an external JavaScript file, Rachna should use the script tag with the attribute src.
<script type="text/javascript" src="ext_code.js"></script>
This script tag should be included between the <head> tags in the HTML document.
226 Touchpad Web Applications-XII

