Question:

How to add number together and despite using parseFloat I still get NaN

Solution

You cannot rely on parseFloat to consistently provide you with a valid number. Although typeof NaN is still a number, the returned type is always a number.

console.log(parseFloat("Invalid Number"));

console.log(typeof NaN);

console.log(typeof parseFloat("Invalid Number"));

console.log(NaN + 100);

You require a backup plan and an extra check in case the outcome is NaN. If you wish to treat them as zeros, for example:

const value = "<<blank/novalue";

const parsedValue = parseFloat(value);

const safeParsedValue = isNaN(parsedValue) ? 0 : parsedValue;

console.log(safeParsedValue);

You might also want a check for too large values since when the number is outside the double-precision 64-bit IEEE 754-2019 the function will return Infinity.

parseFloat("1.7976931348623159e+308"); // Infinity

parseFloat("-1.7976931348623159e+308"); // -Infinity

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