A while ago I've written a custom validation method for .validate(). It is a local validation plugin, with some limited validation.

I was required to write a validation method with the following requirements:

  • Must accept a custom string.
  • Must allow a maximum value.
  • Must allow a minimum value.
  • Has to allow to have dynamic values on the string.
  • Must validate using a regular expression.
  • Must allow numbers in the Portuguese and English formats.

At the time, it was quite a challenge and I was happy with the result, but the code is BAD. It works, but it is so hacky and kludged it hurts my soul.

    var __c_number_between=new String('');

                return 'The value must be between __MIN__ and __MAX__'
        __c_number_between.toString=function(){return this.valueOf();};

            var num=d.replace(/\./g,'').replace(',','.')/1;
            return o.max>=num&&num>=o.min;

Yes, that is the code. It fulfills all my needs, but relies on a really bad behaviour in Javascript, which is that objects are passed as a reference. It also relies on Javascript being executed linearly, instead of having multiple threads, which is REALLY bad!

How can I re-write this in a clean and decent way?

Also, worth noticing is that this is a cross-posting from StackOverflow, on the following question: jQuery .validation plugin: help cleaning aditional method


1 Answer 1



jQuery.validator has a format method

This allows you to replace the String you created entirely.

However, this would require you to replace your 'o' parameter object with an array ( [min,max] ).

        var num=d.replace(/\./g,'').replace(',','.')/1,
            // min/max assigns for context readability (optional)
            min = o[0],
            max = o[1];
        return max>=num&&num>=min;
    },$.validator.format('The value must be between {0} and {1}'));


While the docs say:

The default message to display for this method. Can be a function created by ''jQuery.validator.format(value)''. When undefined, an existing message is used (handy for localization), otherwise the field-specific messages have to be defined.

Any function that returns a string can be used so boom:

        var num=d.replace(/\./g,'').replace(',','.')/1,
        return 0.max>=num&&num>=0.min;
    },function(params){return 'The value must be between {0} and {1}'.replace('{0}',params.min).replace('{1}',params.max);});
  • \$\begingroup\$ Actually, it is o.max and o.min, instead of o[0] and o[1]. But other than that... WOW! I had no idea about that method. It really is a lifesaver! Thank you a lot! Now, I have a few validations to fix. Once again, thank you \$\endgroup\$ Commented Aug 5, 2015 at 18:01
  • \$\begingroup\$ To use $.validator.format the o parameter has to be an array (as far as i know) so {min:y,max: x} is now [x,y]... aleast in how i interpreted your code \$\endgroup\$
    – Shaun H
    Commented Aug 5, 2015 at 18:05
  • \$\begingroup\$ That would be a bad surprise. It isn't feasable to change everything. I have at least 100 instances of that validation. But that is a problem outside the scope of your review, and something I didn't mention. Therefore, you deserved the reputation. I will look into some way to hammer this screw on my steel bar. \$\endgroup\$ Commented Aug 5, 2015 at 18:09

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