ESLint Unexpected use of isNaN

Question

I\'m trying to use the isNaN global function inside an arrow function in a Node.js module but I\'m getting this error:

[eslint] Unexpected use of \'is

Answer 1

In my case, I wanted to treat 5 (integer), 5.4(decimal), '5', '5.4' as numbers but nothing else for example.

If you have the similar requirements, below may work better:

const isNum = num => /^\d+$/.test(num) || /^\d+\.\d+$/.test(num);

//Check your variable if it is a number.
let myNum = 5;
console.log(isNum(myNum))

To include negative numbers:

const isNum = num => /^-?\d+$/.test(num) || /^-?\d+\.\d+$/.test(num);

This will remove your issue of global use of isNaN as well. If you convert the isNum function to a normal ES5 function, it will work on IE browser as well.