jqplot zoom event & change tickets format

/**  jqplot after zoom event*/$('#chart').on('jqplotZoom', function(ev, gridpos, datapos, plot, cursor){      //处理chart放大后的事件});/**  Overwrite  DateTickFormatter function*/$.jqplot.DateTickFormatter = function(format, val) {        if (plot) {            var noDays = days_between(new Date(plot.axes.xaxis.max), new Date(plot.axes.xaxis.min));            console.log("days_between = " + noDays);            if (noDays < 28) format = "%d";            else if (noDays < 120) format = '%m/%d';            else format = '%Y/%m/%d';        }        return $.jsDate.strftime(val, format);};