Good Form, Jack - Prevent Annoying Error Messages
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You and I spend a good deal of time ensuring that people have entered the proper data types into the fields of a form. In fact, we even think of pleasant error messages, such as: “Excuse me Sir/Madam, you seem to have entered an incorrect date. Please be so kind as to enter the date in this format...” You see, we know that we need the date to be entered as DD/MM/YYYY, and we've prevented any programming errors by telling them so politely. But it will still be bothersome for the user to now go back, and change the field from "tomorrow" to the proper format.
So how do we ensure that they're typing in data as we need it, before they even try to submit the form? Well, if you want, you could always just stand behind them and watch over their shoulder, even slap their hands if they mistype. You can call me crazy, but I'd much prefer a programmatic solution.
In the case of date fields, it's very simple to ensure proper input. You just don't let them type anything in! It's that simple, you just add the readonly attribute to the input field. Of course they need some method to enter the date, which we provide ever so graciously with a JavaScript calendar. The reason for this is that you can configure in your code exactly how you want the date to be entered, and the calendar will consistently comply. Instead of wasting time creating your own calendar, you can download this slick tool: http://www.softcomplex.com/products/tigra_calendar/
Another area you would want to monitor input is with number fields. Whether currency, phone numbers, whatever, all you want in that field are the integers between 0-9, and maybe a period. You can find a quick tool to limit the input to integers here: http://www.devarticles.com/c/a/JavaScript/Universal-Form-Validation/3/
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