Проверка положительного числа в jQuery

Have you considered to use anything beside regular expressions?

If you are using the jQuery Validation Plugin you could create a custom validation method using the Validator/addMethod function:

$.validator.addMethod('positiveNumber',
    function (value) { 
        return Number(value) > 0;
    }, 'Enter a positive number.');

Edit: Since you want only regular expressions, try this one:

^\+?[0-9]*\.?[0-9]+$

Explanation:

• Begin of string (^)
• Optional + sign (\+?)
• The number integer part ([0-9]*)
• An optional dot (\.?)
• Optional floating point part ([0-9]+)
• End of string ($)