Tak*_*son 9 javascript jquery d3.js
我正在学习D3并且使用select运算符遇到了一个问题.
具体来说,为什么以下代码将<p>元素添加到正文之外,而不是在其中？
var pData1 = d3.select("body").select("p").data([1]).enter().append("p");
我正在使用一个完全空白的HTML文件,只有<head>和<body>标签来测试.
<html lang="en">
<head>
<title><!-- Insert your title here --></title>
<script type="text/javascript" src="d3.min.js"></script>
</head>
<body>
</body>
</html>
Ame*_*aBR 13
(这重复了Lars Kotthoff的答案中的内容,但我花时间创建了演示,所以我想我还会发帖.)
问题在于select,selectAll不会重新定义enter()选择中添加的元素的父元素.
d3.select("body").select("p#a")
.data([1])
.enter().append("p").attr("id", "a")
.text("This paragraph is appended to <html> (the document root)
because no selectAll statement reset the parent element.");
d3.selectAll("p#b")
.data([1])
.enter().append("p").attr("id", "b")
.text("This paragraph is appended to <html>
because the selectAll statement is called directly on the root.");
d3.selectAll("body").select("p#c")
.data([1])
.enter().append("p").attr("id", "c")
.text("This paragraph is also appended to <html>
because the last selectAll statement was called directly from the root.");
d3.select("body").selectAll("p#d")
.data([1])
.enter().append("p").attr("id", "d")
.text("This paragraph is appended to <body>
because the selectAll statement is a sub-selection of the body selection.");
d3.selectAll("body").selectAll("p#e")
.data([1])
.enter().append("p").attr("id", "e")
.text("This paragraph is also appended to <body>
because the final selectAll statement is a sub-selection of the body.");
http://fiddle.jshell.net/eLF4H/
在select语句之后使用输入链是不常见的(与selectAll相比),因为如果要进行数据连接,通常会选择多个元素.但是,如果要创建元素(如果它不存在)或者更新它,则有两个选项:
使用selectAll语句后跟数据连接
var pdata1 = d3.select("body").selectAll("p#data")
//select element if it exists
.data([dataObject]);
//join to the current data
pdata1.enter().append("p").attr("id", "data");
//create element if required
pdata1.text(function(d){return d.textValue;});
//set or update the element based on the data
如果需要,使用if语句创建元素并用于.datum()绑定数据
var pdata1 = d3.select("p#data")
//select element if it exists
if ( pdata1.empty() ) {
pdata1 = d3.select("body").append("p").attr("id", "data");
//create element if required
}
pdata1.datum(dataObject)
//note that you don't need to put the data into an array
.text(function(d){return d.textValue;});
//set or update the element based on the data