I want to use the HTML5 date input field
<input type='date' name='customDate'>
So that other users can make use of the build-in datepicker from their browser.
I would like to check if the input is actually in date format. As I found here: Is there any way to change input type="date" format? there is no unique presentation format. For example, in Chrome the input of the date field is given in the form of dd.mm.yyyy and in Firefox 24 or IE 9/10 the date in the input field is presented as YYYY-MM-DD.
My first problem is, how do you tell the user in which format you want him to type in the date? In Firefox I would need something like
<label>Enter Date(YYYY-MM-DD)</label><input type='date'
name='customDate' placeholder='YYYY-MM-DD'>
But this would be wrong for Chrome.
Secondly, how can I check before submission if the current input is in the valid date format (of the browser)? I know that I could check with PHP after submit if the date format is given as YYYY-MM-DD, but how do you check it with JavaScript before submission?