for (var i = 0; i < barValues.length; i++) { actualBarHeight = Math.floor((barValues[i] / chartMaxY) * barchartHeight); var barChartID = \"#barChart\"
You could try caching the span selector, like so:
var barChartID = "#barChart" + (i+1) var span = $(barChartID + " .value span"); span.css('background-color','transparent'); $(barChartID + " img").animate({ height: actualBarHeight }, 500, function() { span.css('background-color','white'); });