Determine whether a string is numeric in JavaScript

This post will discuss how to determine whether a string is numeric in JavaScript.

1. Using `isNaN()` method

The recommended solution is to use the isNaN() method, which tests a value for NaN (Not a Number). To illustrate, consider the following code, where the isNumeric() returns true when the given string is a number and false otherwise.

const isNumeric = n => !isNaN(n);

/* Numeric strings */

isNumeric('1');

isNumeric('+1');

isNumeric('-1');

isNumeric('1.0');

isNumeric('1.1');

isNumeric('1e10');

isNumeric('2e-5');

isNumeric('0xFFFFFF');

isNumeric('Infinity');

isNumeric('-Infinity');

/* Non-Numeric strings */

isNumeric('NaN');

isNumeric('str1');

2. Using `Number()` function

A simple and fairly efficient solution to convert the given string to a numerical value is using Number as a function, which returns NaN if it cannot be converted into a number.

This is demonstrated below, where we cast the return value of the Number() function to be boolean using !!expr.

const isNumeric = n => !!Number(n);