Check if a value is a number in JavaScript
Question:
How to check if a value is a number in JavaScript? Answer:
const value = 100;
if (typeof value === 'number') {
console.log(`${value} is a number`);
}Description:
There are multiple ways how you can check if a variable contains a number or not in JavaScript. The options are:
The typeof operator
The simplest way is to use the typeof operator like this:
typeof value === 'number'The isNaN method
With the built-in isNaN method, you can check the opposite. This method returns true if the value is NOT a number.
isNaN(value);The Number.isFinite, Number.isInteger
Using the isFinite and isInteger methods on the Number object you can check if a value is a finite number or an integer:
Number.isFinite(value);Check if a string contains a valid number
In the case of form submission, you get all values as strings. In such cases, the solutions above will not work. Instead, you can use the parseInt method and create a small helper function like this:
function isNumeric(str) {
return !isNaN(parseInt(str));
}
Reference:
JavaScript typeof reference
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Tags:
value, variable, number, check, test, JavaScript Technical term:
Check if a value is a number in JavaScript