Javascript returning NaN

Question

I\'m attempting to display a subtotal each time a customer enters a quantity. However, when I loop through my inputs, I get a NaN as the total. I believe it may

Answer 1

parseFloat and parseInt can return NaN if the first character of the string cannot be converted to a number.

So, I would safeguard against it like this (NaN is a falsy value):

price = parseFloat(price) || 0;
qty = parseInt(qty, 10) || 0;

Arithmetic operations on numbers with the value NaN almost always result in NaN (NaN + 5 will result in NaN.) That means, if only one of the input cannot be parsed by parseFloat or parseInt, your current code would end up calculating NaN for the subtotal.

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It's already been mentioned in the comments (by Felix mostly) but I think it's worth the emphasis as these are important concerns:

• Always pass the radix argument to the parseInt function;
• Do not use class for variable names: It's a reserved (not used, but reserved) keyword;
• Don't expect the subtotal to be perfectly accurate unless you do your calculations in cents.