select（）和selectAll（）之间有什么区别 [英] What is the difference between select() and selectAll()

问题描述

select（）和selectAll（）有什么区别？

What is the difference between select() and selectAll()?

为什么第二个不附加ap标签？

Why doesn't the second one append a p tag?

divSelection = d3.select('#div-vis').selectAll('p').data(['dummy']).enter().append('p');

divSelection = d3.select('#div-vis').select('p').data(['dummy']).enter().append('p');

推荐答案

来自嵌套选择：

嵌套选择有另一个微妙但关键的副作用：它为每个组设置父节点。父节点是选择的隐藏属性，用于确定添加输入元素的位置。 ... select和selectAll之间有一个重要的区别：select保留现有的分组，而selectAll创建一个新的分组。因此调用select会保留原始选择的数据，索引甚至父节点！

Nesting selections has another subtle yet critical side-effect: it sets the parent node for each group. The parent node is a hidden property on selections that determines where to append entering elements. … There is an important difference between select and selectAll: select preserves the existing grouping, whereas selectAll creates a new grouping. Calling select thus preserves the data, index and even the parent node of the original selection!

当你说 d3.select（＃vis），选择的父节点仍然是文档元素。然后，当您说 selectAll（p）时，将父节点定义为先前选择的#vis元素，因为selectAll是嵌套运算符。这只发生在selectAll而不是select。

When you say d3.select("#vis"), the parent node of the selection is still the document element. When you then say selectAll("p"), you define the parent node as the previously-selected #vis element, because selectAll is a nesting operator. That only happens with selectAll and not select.

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