学步园

Simple selection in DOM ranges
The simplest way to select a part of the document using a range isto use either selectNode() or selectNodeContents(). These methodseach accept one argument, a DOM node, and fill a range withinformation from that node.
The selectNode() method selects the entire node, including itschildren, whereas
selectNodeContents() selects all of the node’s children.
DOM ranges中的简单选中：
 使用的range选中文档的一部分的最简单方法是使用selectNode()或者selectNodeContents()。这些方法都接受一个参数,(一个DOM节点)并且用这个节点的信息填充这个range。
  selectNode()选中整个节点包含它的子节点，selectNodeContents()选中所有它的子节点。

Whenever you create a range, a number of properties are assigned toit:
1，startContainer — The node within which the range starts (theparent of the first node in the selection)
2，startOffset — The offset within the startContainer where therange starts. If
startContainer is a text node, comment node, or CData node, thestartOffset is the number of characters skipped before the rangestarts; otherwise, the offset is the index of the first child nodein the range.
3，endContainer — The node within which the range ends (the parentof the last node in the selection)
4，endOffset — The offset within the endContainer where the rangeends (follows the same rules as startOffset)
5，commonAncestorContainer — The first node within which bothstartContainer and
endContainer exist
These properties are all read-only and are designed to give youadditional information about the range.
  当你创建range的时候，许多属性被赋给它：
1，startContainer-range开始的节点（选中区的第一个节点的父节点）。
2，startOffset-在range开始的startContainer里面的offset。假如startContainer是一个文本节点，注释节点或者CData节点，startOffset是range开始前跳过的字母的数量；否则offset是range第一个子节点的索引。
3，endContainer-range结束的节点（选中区的最后节点的父节点）
4，endOffset-在range结束的endContainer里面的offset。（遵循startOffset规则）
5，commonAncestorContainer-startContainer和endContainer都存在其中的第一个节点。
  这些属性都是只读的，被设计出来给你关于range详细的信息。
When you use selectNode(), the startContainer, endContainer, andcommonAncestorContainer are all equal to the parent node of thenode that was passed in; startOffset is equal to the index of thegiven node within the parent’s childNodes collection, whereasendOffset
is equal to the startOffset plus one (because only onenode is selected).
  当你使用selectNode()时， startContainer, endContainer,和commonAncestorContainer都等于选中节点的父节点。startOffset等于选中节点在父节点中所有子节点的索引。同时endOffset等于startOffset加一（因为只用一个节点被选中）。
When you use selectNodeContents(), startContainer, endContainer,and commonAncestor Container are equal to the node that was passedin; startOffset is equal to 0; endOffset is equal to the number ofchild nodes (node.childNodes.length).
  当你使用selectNodeContents()时，startContainer,endContainer,和commonAncestorContainer都等于被选中的节点；startOffset等于零，endOffset等于子节点的长度（node.childNodes.length）。