jquery.dataspy.js

// Usage
// $.dataSpy()
// $(document).bind('data.change', function(){console.log('data changed')} )
// $(document).bind('data.unchange', function(){console.log('data unchanged')} )


(function($) {
    
    function hash(data, n) {
        var norm = Math.pow(2, -32);
        var a = 2095533;
        var s = 0, c = 1;
        var t, t0 = 0;
        
        data = data.toString();
        for (var i = 0; i < data.length; i++) {
            s -= data.charCodeAt(i) * 65537 * norm;
            if (s < 0) {
                s += 1;
            }
            t = a * s + c * norm;
            t0 = s = t - (c = t | 0);
            t = a * s + c * norm;
            s = t - (c = t | 0);
        };
        
        if (n) {
            return Math.floor(n * (s + t0 * norm));
        } else {
            return s + t0 * norm;
        };
    };
    
    $.dataSpy = function(settings) {
        var config = {
            'changeEvent': 'data.change', 
            'undoEvent': 'data.unchanged', 
            'hasher': hash,
            'selector': 'input textarea select'
        };
        
        if (settings) $.extend(config, settings);
        
        function concat_values(elements){
            var data = '';
            elements.each(function(){
                data = data + this.val();
            });
            return data;
        };
        
        var initial_values = concat_values($(config.selector));
        var initial_hash = config.hasher(initial_values);
        
        // Bind to onchange for all elements. TODO: Use .live()
        data_elements.bind('change', function(){
            var values = concat_values($(config.selector));
            var h = config.hasher(values);
            if (h != initial_hash) {
                $(document).trigger(config.changeEvent);
            } else {
                $(document).trigger(config.undoEvent);
            };
        });
        
    };

})(jQuery);