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 'isNaN'. (no-restricted-globals)
This is my code:
const isNumber = value => !isNaN(parseFloat(value));
module.exports = {
isNumber,
};
Any idea on what am I doing wrong?
PS: I'm using the AirBnB style guide.
As the documentation suggests, use Number.isNaN.
const isNumber = value => !Number.isNaN(Number(value));
Quoting Airbnb's documentation:
Why? The global isNaN coerces non-numbers to numbers, returning true for anything that coerces to NaN. If this behavior is desired, make it explicit.
// bad
isNaN('1.2'); // false
isNaN('1.2.3'); // true
// good
Number.isNaN('1.2.3'); // false
Number.isNaN(Number('1.2.3')); // true
@Andy Gaskell isNumber('1.2.3') return true, you might want to edit your answer and use Number() in place of parseFloat()
const isEmpty = value => typeof value === 'undefined' || value === null || value === false;
const isNumeric = value => !isEmpty(value) && !Number.isNaN(Number(value));
console.log(isNumeric('5')); // true
console.log(isNumeric('-5')); // true
console.log(isNumeric('5.5')); // true
console.log(isNumeric('5.5.5')); // false
console.log(isNumeric(null)); // false
console.log(isNumeric(undefined)); // false
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.
