jquery - How can I validate that the max field is greater than the min field?

Question

I have a few sets of min and max fields in a form, where the user can specify a range by filling in a min and a max. I'm using jQuery's Validate plugin for my form validation. I'd like to set up a validation rule that enforces that the max field is greater than the min. This would be invoked whenever the max or the min fields values are changed.

I know I can set up some sort of basic custom validation method like this:

$.validator.addMethod("greaterThan",
    function(value, max, min){
        return parseInt(value) > parseInt($(min).val());
    }, "Max must be greater than min"
);

And then add a rule for the max element:

rules: {
    maxTruck: {greaterThan: '#minTruck'}
}

But it's a bit more complicated because this only applies when the max field is changed, not the min. Is there any simple way to do this without having to write a lessThan method and apply that to the min field?

And then another thing I'd like to tackle - is there any simple way that I can apply this generically instead of having to enumerate each max field and which min it maps to? So that I can just have a min and max class and call something like:

$(".max").rules('add', { greaterThan: ".min" });

And somehow set up the method to be able to figure out (maybe based on a shared attribute?) which min the max field is paired with?

Update:

The basic logic that I mentioned in this post can be seen in this jsfiddle. However, I have not really worked on this much - I am looking for the logic to basically link sets of min and max fields the way I described. And I don't know if this is the best way to do this - as I mentioned, I'd love to be able to do this generically so that I don't have to refer to the min and max fields by id.

Answer 1

Ok, here's something that should work. The rule is based on the built in equalTo method:

$.validator.addMethod("greaterThan", function (value, element, param) {
    var $min = $(param);

    if (this.settings.onfocusout) {
        $min.off(".validate-greaterThan").on("blur.validate-greaterThan", function () {
            $(element).valid();
        });
    }

    return parseInt(value) > parseInt($min.val());
}, "Max must be greater than min");

Example: http://jsfiddle.net/tUPQc/2/

---

To make the rule a bit more generic, you'll have to need to use addClassRules:

$.validator.addMethod("greaterThan", function (value, element, param) {
    var $element = $(element)
        , $min;

    if (typeof(param) === "string") {
        $min = $(param);
    } else {
        $min = $("#" + $element.data("min"));
    }

    if (this.settings.onfocusout) {
        $min.off(".validate-greaterThan").on("blur.validate-greaterThan", function () {
            $element.valid();
        });
    }
    return parseInt(value) > parseInt($min.val());
}, "Max must be greater than min");

$.validator.addClassRules({
    greaterThan: {
        greaterThan: true
    }
});

Then in your HTML:

<input id="maxTruck" name="maxTruck" type="text" class="number greaterThan" data-min="minTruck" />

Example: http://jsfiddle.net/tUPQc/3/