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I want to validate an HTML form to ensure an <input> has a value. In JavaScript, what is the value of an empty field in a form: null or the empty string ("")?

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    did you try to see for yourself what it was??? Commented Apr 29, 2011 at 18:21
  • Seems like it would be fairly simple to test both of these methods. Did you try it already and are getting ambiguous results? Commented Apr 29, 2011 at 18:22
  • SO shouldn't be your first choice. Try yourself and if you think you are unable to find out and you really need a help, try SO. Help keep SO clean. Commented Apr 29, 2011 at 18:25
  • You could always alert or log document.getElementById(idname).value to see the value. Commented Apr 29, 2011 at 18:25
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    No I didn't try it myself. There are a lot of examples online that give different answers, so I wanted to ask the experts, in case there are cross-browser compatibility issues or other snafus. Commented Apr 29, 2011 at 18:30

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For any input element, value is always a string. This means you can expect it to be "", when empty.

See the docs for HTMLInputElement on the Mozilla Developer Network, or the relevant part of the HTML4 spec.

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Empty string, if it's a text field.

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It's an empty string -- one of the beautiful perks of JavaScript.

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