d3.js学习6

加载server数据d3.json(url,callback)

---

首先准备一些json数据，将上一篇的js数据转化为json格式并存储

var data=[
	{expense:10,category:"Retail"},
	{expense:15,category:"Gas"},
	{expense:30,category:"Retail"},
	{expense:50,category:"Dining"},
	{expense:80,category:"Gas"},
	{expense:65,category:"Retail"},
	{expense:55,category:"Gas"},
	{expense:30,category:"Dining"},
	{expense:20,category:"Retail"},
	{expense:10,category:"Dining"},
	{expense:8,category:"Gas"}
];

var jsonData=JSON.stringify(data);
document.write(jsonData);

输出结果后存储为data.json

var data=[];

function render(data,comparator){
	var selection=d3.select("body")
	.selectAll("div.h-bar")
	.data(data);
	//enter
	selection.enter()
	.append("div")
	.attr("class","h-bar")
	.append("span");
	//remove
	selection.exit().remove();
	//update
	selection.attr("class","h-bar")
	.style("width",function(d){
		return (d.expense*5)+"px";
	})
	.select("span")
	.text(function(d){
		return d.category;
	});
}

//d3.json('url',callback)
function load(){
	d3.json("data.json",function(error,json){
	data=data.concat(json);
	render(data);
	})
}