javascript - 未捕获的类型错误 : Cannot read property 'length' of undefined in d3. js-6ren

javascript - 未捕获的类型错误 : Cannot read property 'length' of undefined in d3. js

转载作者：行者123 更新时间：2023-11-30 05:44:11

*我是 d3.js 的新手，正在尝试使用 json 文件绘制折线图，但出现错误，请有人帮助我。我哪里出错了。

实际上，我尝试了不同的文件格式，如 .csv 和 .tsv，但仍然出现相同的错误...

错误:未捕获类型错误:无法读取未定义的属性“长度”。

代码:

<!DOCTYPE html>
<meta charset="utf-8">
<style>
 body {font: 10px sans-serif;}
 .axis path,
 .axis line {
  fill: none;
  stroke: #000;
  shape-rendering: crispEdges;
 }
.x.axis path {display: none;}
.line {fill: none;
       stroke: steelblue;
       stroke-width: 1.5px;
      }
</style>
<body>
<script src="http://code.jquery.com/jquery-1.8.2.min.js"></script>
<script src="http://d3js.org/d3.v2.js"></script>
<script>
var arrData = [
   {
    "Engine": "L0",
    "date": "01-Aug-13",
    "value": 37.92625
},
{
    "Engine": "L0",
    "date": "02-Aug-13",
    "value": 39.19708333
},
{
    "Engine": "L1",
    "date": "01-Aug-13",
    "value": 44.13875
},
{
    "Engine": "L1",
    "date": "02-Aug-13",
    "value": 43.15
},
{
    "Engine": "L2",
    "date": "01-Aug-13",
    "value": 34.765
}];
 
var margin = {top: 20, right: 20, bottom: 30, left: 50},
width = 960 - margin.left - margin.right,
height = 500 - margin.top - margin.bottom;

var parseDate = d3.time.format.utc("%d-%b-%y").parse;

var x = d3.time.scale()
.range([0, width])

var y = d3.scale.linear()
.range([height, 0]);

var xAxis = d3.svg.axis()
.scale(x)
.orient("bottom");

 var yAxis = d3.svg.axis()
.scale(y)
.orient("left");

 var line = d3.svg.line()
.x(function(d) { return x(d.date); })
.y(function(d) { return y(d.value); });

 var svg = d3.select("body").append("svg")
.attr("width", width + margin.left + margin.right)
.attr("height", height + margin.top + margin.bottom)
.append("g")
.attr("transform", "translate(" + margin.left + "," + margin.top + ")");

 var data = arrData.map(function(d) {
  return {
    Engine:d[0],
     date: parseDate(d[1]),
     value: d[2]
  };
  
 });
 x.domain(d3.extent(data, function(d) { return d.date; }));
 y.domain(d3.extent(data, function(d) { return d.value; }));
 
 svg.append("g")
 .attr("class", "x axis")
 .attr("transform", "translate(0," + height + ")")
 .call(xAxis);
  
 svg.append("g")
 .attr("class", "y axis")
  .call(yAxis)
 .append("text")
  .attr("transform", "rotate(-90)")
  .attr("y", 6)
  .attr("dy", ".71em")
  .style("text-anchor", "end")
  .text("Price ($)");

   svg.append("path")
   .datum(data)
   .attr("class", "line")
   .attr("d", line);
   
  </script>
  </body>

最佳答案

更改这段脚本...

var data = arrData.map(function(d) {
    return {
        Engine:d[0],
        date: parseDate(d[1]),
        value: d[2]
    };
});

到

var data = arrData.map(function(d) {
    return {
        Engine: d["Engine"],
        date: parseDate(d["date"]),
        value: d["value"]
    };
});

当它们实际上是属性时，您试图通过索引获取值，因此它们之前返回 undefined。

实际上是 parseDate() 返回了错误消息。传递正确的值可以修复它。

Here's a fixed and working example...

关于javascript - 未捕获的类型错误 : Cannot read property 'length' of undefined in d3. js，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/18917451/