text: <!DOCTYPE html>
  <html>
  	<head>
  		<meta charset="UTF-8" content="">
  		<title>core - selection.text([value])</title>
  		<script type="text/javascript" src="../../d3.js"></script>
  	</head>
  	<body>
  		<script type="text/javascript">
  			d3.select('body').text("selection.text([value])");	//设置元素的文本	
  			d3.select('body')
  				.text(function(){ 
  					return "new text: "+d3.select(this).text();
  				});	//设置元素的文本				
  		</script>
  	</body>
  </html>