Only allow a single dot point in input field
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I have an input field which has:

    $(".double").alphanumeric({allow:" ",ichars:"`~!@#$%^&*=_+[]\\{}|;\":,/<>?'-()\/abcdefghijklmnopqrstuvwxyzABCDFEGHIJKLMNOPQRSTUVWXYZ"});

validation applied to it.

I need to further restrict entry so that only a single decimal place can be added e.g. 100.00 or 255.95

The input is used for currency so I need to only allow 1 decimal point. At the moment its allow 100.00.00 which messes up the system!

Thanks