本文介绍如何使用amCharts插件绘制柱形图，并通过在AmCharts.AmGraph中设置labelText属性为[[value]]，实现默认显示每个柱子数值的功能。
amCharts柱形图默认显示数值配置
本文通过实例演示了如何利用JS插件amCharts绘制柱形图，并实现默认显示数值的配置方法，供读者参考学习。
在使用amCharts.js构建柱形图（column chart）时，经常需要在图表中直接显示每个柱子的具体数值。
实现该功能的关键在于AmCharts.AmGraph配置，只需将labelText属性设置为[[value]]即可达成目标。
配置生效后的图表效果如图所示：
具体实现代码如下：
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>amCharts examples</title>
<link rel="stylesheet" href="style.css" rel="external nofollow" type="text/css">
<script src="http://www.amcharts.com/lib/3/amcharts.js" type="text/javascript"></script>
<script src="http://www.amcharts.com/lib/3/serial.js" type="text/javascript"></script>
<script src="http://www.amcharts.com/lib/3/themes/light.js"></script>
<script>
var chart;
var chartData = [
{
"country": "China",
"visits": 2325
},
{
"country": "USA",
"visits": 1822
},
{
"country": "Japan",
"visits": 1809
},
{
"country": "Germany",
"visits": 1322
},
{
"country": "UK",
"visits": 1122
},
{
"country": "France",
"visits": 1114
}
];
AmCharts.ready(function () {
// SERIAL CHART
chart = new AmCharts.AmSerialChart(AmCharts.themes.light);
chart.dataProvider = chartData;
chart.categoryField = "country";
chart.startDuration = 1;
// AXES
// category
var categoryAxis = chart.categoryAxis;
categoryAxis.labelRotation = 90;
categoryAxis.gridPosition = "start";
// value
// in case you don't want to change default settings of value axis,
// you don't need to create it, as one value axis is created automatically.
// GRAPH
var graph = new AmCharts.AmGraph();
graph.valueField = "visits";
graph.balloonText = "[[category]]: <b>[[value]]</b>";
graph.type = "column";
graph.lineAlpha = 0;
graph.fillAlphas = 0.8;
// display label text on each column
graph.labelText = "[[value]]";
chart.addGraph(graph);
// CURSOR
var chartCursor = new AmCharts.ChartCursor();
chartCursor.cursorAlpha = 0;
chartCursor.zoomable = false;
chartCursor.categoryBalloonEnabled = false;
chart.addChartCursor(chartCursor);
chart.creditsPosition = "top-right";
chart.write("chartdiv");
});
</script>
</head>
<body>
<div id="chartdiv" style="width: 100%; height: 300px;"></div>
</body>
</html>
读者可通过在线HTML/CSS/JavaScript代码运行工具：http://tools.jb51.net/code/HtmlJsRun来测试上述代码的实际运行效果。
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