D3不会加载树状图

我正在尝试使用D3和JSON文件来创建和显示树映射。非常简单，只是为了好玩而尝试D3。然而，在我把tree.js和运行脚本放在一起之后，我会得到一个空白页面。控制台显示

XMLHttpRequest cannot load file:///Users/aczre/Desktop/d3TestApp/shreleases.json.
Cross origin requests are only supported for HTTP.
Uncaught TypeError: Cannot read property 'children' of null d3.v2.js:6081
d3_layout_hierarchyChildren d3.v2.js:6081
 recurse d3.v2.js:5990
 hierarchy d3.v2.js:6033
 tree d3.v2.js:6384
 object.nodes d3.v2.js:6074
 (anonymous function) tree.js:17
 d3.json d3.v2.js:514
 ready d3.v2.js:504
 d3.xhr.req.onreadystatechange d3.v2.js:497
 d3.xhr d3.v2.js:500
 d3.text d3.v2.js:510
 d3.json d3.v2.js:513
 (anonymous function) tree.js:16
Uncaught Error: NETWORK_ERR: XMLHttpRequest Exception 101 d3.v2.js:500
 d3.xhr d3.v2.js:500
 d3.text d3.v2.js:510
 d3.json d3.v2.js:513
 (anonymous function) tree.js:16

不确定我做错了什么。。。这是我的tree.js

var width = 960,
    height = 2000;
var tree = d3.layout.tree()
    .size([height, width - 160]);
var diagonal = d3.svg.diagonal()
    .projection(function(d) { return [d.y, d.x]; });
var vis = d3.select("#chart").append("svg")
    .attr("width", width)
    .attr("height", height)
    .append("g")
    .attr("transform", "translate(40, 0)");
d3.json("shreleases.json", function(json) { // Line 16
  var nodes = tree.nodes(json);
  var link = vis.selectAll("path.link")
  .data(tree.links(nodes))
.enter().append("path")
  .attr("class", "link")
  .attr("d", diagonal);
  var node = vis.selectAll("g.node")
      .data(nodes)
     .enter().append("g")
      .attr("class", "node")
      .attr("transform", function(d) { return "translate(" + d.y + "," + d.x + ")"; })
  node.append("circle")
      .attr("r", 4.5);
  node.append("text")
      .attr("dx", function(d) { return d.children ? -8 : 8; })
      .attr("dy", 3)
      .attr("text-anchor", function(d) { return d.children ? "end" : "start"; })
      .text(function(d) { return d.name; });
});

我试着坚持D3网站上列出的例子，https://github.com/mbostock/d3/wiki/Gallery但我不确定我是否完全理解语法。