how to make the Textbox to allow only three digits with three decimal points?

I want to make the text开发者_运维知识库box allow only three digits and three decimals.For example 999.999.similarly it doesnt allow any characters like a,b,/,etc.How can I do with the Jquery?

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Have you looked at the jQuery.validate plugin?

$('#formid').validate({
    rules: {
        fieldname: {
            required:function(element) {
                return /^\s*[0-9]{,3}(?:\.[0-9]{1,3})?\s*$/.test(element.value);
            }
        }
    }
});

EDIT: admittedly I didn't test the regex and merely wanted to demonstrate how it works. Updated regex as per nickf's suggestion, thanks.

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Take a look at jQuery numeric plugin.

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You could also look at this masked input plugin