How do I check that a number is float or integer?

Method 1: Using Number.isInteger() Function

This is the most straightforward method to check if a number is an integer. The Number.isInteger() method returns a boolean value indicating whether the provided value is an integer.

javascript
function checkNumberType(num) {
  if (Number.isInteger(num)) {
    return `${num} is an integer`;
  } else {
    return `${num} is a float`;
  }
}

console.log(checkNumberType(10)); // Output: 10 is an integer
console.log(checkNumberType(10.5)); // Output: 10.5 is a float

Method 2: Using the Modulo Operator %

Another approach is to use the modulo operator %. If the remainder when dividing the number by 1 is zero, it is an integer; otherwise, it is a float.

javascript
function checkNumberType(num) {
  if (num % 1 === 0) {
    return `${num} is an integer`;
  } else {
    return `${num} is a float`;
  }
}

console.log(checkNumberType(10)); // Output: 10 is an integer
console.log(checkNumberType(10.1)); // Output: 10.1 is a float

Method 3: Using Math.floor() or Math.ceil() Methods

By comparing the number with its floor or ceiling value. If both are equal, it is an integer; otherwise, it is a float.

javascript
function checkNumberType(num) {
  if (Math.floor(num) === num) {
    return `${num} is an integer`;
  } else {
    return `${num} is a float`;
  }
}

console.log(checkNumberType(12)); // Output: 12 is an integer
console.log(checkNumberType(12.3)); // Output: 12.3 is a float

Summary

The following are several common methods in JavaScript for checking if a number is an integer. Number.isInteger() is the most concise and modern approach, and is generally recommended. However, other methods like using % or Math.floor() can be useful in specific scenarios, particularly when compatibility is a concern.