Question

I am pulling a value via JavaScript from a textbox. If the textbox is empty, it returns NaN. I want to return an empty string if it’s null, empty, etc.

What check do I do? if(NAN = tb.value)?

Answer 1

Hm, something is fishy here.

In what browser does an empty textbox return NaN? I’ve never seen that happen, and I cannot reproduce it.

The value of a text box is, in fact a string. An empty text box returns an empty string!

Oh, and to check if something is NaN, you should use:

if (isNaN(tb.value)) {    ... } 

Note: The isNaN()-function returns true for anything that cannot be parsed as a number, except for empty strings. That means it’s a good check for numeric input (much easier than regexes):

if (tb.value != '' && !isNaN(tb.value)) {    // It's a number    numValue = parseFloat(tb.value); }