Question 7

Question

Can you explain how to use Number.isFinite(), Number.isNaN(), and Number.isInteger() for type checking?

Answer

Those methods are essential tools in JavaScript when dealing with numbers, allowing you to accurately check their types and properties.

Here's a breakdown of each:

1. Number.isFinite(number)

• Purpose: Determines if a value is a finite number (a normal number that doesn't include infinity or NaN).

• Return Value: Returns true if the value is a finite number, and false otherwise.

• Example:

  console.log(Number.isFinite(5));         // Output: true
  console.log(Number.isFinite(Infinity));  // Output: false
  console.log(Number.isFinite(-10.5));      // Output: true
  console.log(Number.isFinite('hello'));    // Output: false 

2. Number.isNaN(number)

• Purpose: Checks if a value is NaN (Not a Number), which represents an undefined or unrepresentable numerical value.

• Return Value: Returns true if the value is NaN, and false otherwise.

• Example:

  console.log(Number.isNaN(NaN));            // Output: true
  console.log(Number.isNaN(123));          // Output: false
  console.log(Number.isNaN('hello'));       // Output: true
  console.log(Number.isNaN(Infinity));      // Output: false 

3. Number.isInteger(number)

• Purpose: Determines if a value is an exact whole number (an integer). It doesn't consider fractions or decimals.

• Return Value: Returns true if the value is an integer, and false otherwise.

• Example:

  console.log(Number.isInteger(5));       // Output: true
  console.log(Number.isInteger(3.14));     // Output: false
  console.log(Number.isInteger(-7));      // Output: true

Why Use These Methods?

• Robustness: Number.isFinite(), Number.isNaN(), and Number.isInteger() provide reliable type checks that handle various edge cases better than simply using typeof or direct comparisons.