How to Check if a Variable is an Integer in JavaScript

To check if a variable is an integer in JavaScript, use Number.isInteger(). Number.isInteger() returns true or false depending on the parameter provided.

let example = 12.1;
Number.isInteger(example); // false
example = 12;
Number.isInteger(example); // true
example = Infinity;
Number.isInteger(example); // false

Non-numeric values will return false, even if the value is an instance of the Number class.

Number.isInteger(null); // false
Number.isInteger('42'); // false
Number.isInteger(new Number(5)); // false

Remember that JavaScript can only represent up to 16 decimal places, so Number.isInteger() may return surprising results in cases where JavaScript doesn't have sufficient numeric precision to represent the output.

let example = 5 + 1e-16;
Number.isInteger(example); // true

example = 5 + 5e-16;
Number.isInteger(example); // false

---

More Fundamentals Tutorials

• Calculate the Median of an Array in JavaScript
• The encodeURIComponent() Function in JavaScript
• How to Check if a Date is Between Two Dates in JavaScript
• Check a String for Numbers in JavaScript
• Rename Variables When Using Object Destructuring in JavaScript
• Split on Multiple Characters in JavaScript
• Empty Objects are Truthy in JavaScript?