如果光標位于新段落的開頭，則使用字符偏移不起作用。下面的方法遍歷DOM節點并將所有節點計入偏移量。它還可以單獨處理開始和結束，以確保選擇記住其確切位置。這是我在一個主要項目中使用的更新版本（參見最后的函數）：
/*
Gets the offset of a node within another node. Text nodes are
counted a n where n is the length. Entering (or passing) an
element is one offset. Exiting is 0.
*/var getNodeOffset = function(start, dest) {
var offset = 0;
var node = start;
var stack = [];
while (true) {
if (node === dest) {
return offset;
}
// Go into children
if (node.firstChild) {
// Going into first one doesn't count
if (node !== start)
offset += 1;
stack.push(node);
node = node.firstChild;
}
// If can go to next sibling
else if (stack.length > 0 && node.nextSibling) {
// If text, count length (plus 1)
if (node.nodeType === 3)
offset += node.nodeValue.length + 1;
else
offset += 1;
node = node.nextSibling;
}
else {
// If text, count length
if (node.nodeType === 3)
offset += node.nodeValue.length + 1;
else
offset += 1;
// No children or siblings, move up stack
while (true) {
if (stack.length <= 1)
return offset;
var next = stack.pop();
// Go to sibling
if (next.nextSibling) {
node = next.nextSibling;
break;
}
}
}
}};// Calculate the total offsets of a nodevar calculateNodeOffset = function(node) {
var offset = 0;
// If text, count length
if (node.nodeType === 3)
offset += node.nodeValue.length + 1;
else
offset += 1;
if (node.childNodes) {
for (var i=0;i<node.childNodes.length;i++) {
offset += calculateNodeOffset(node.childNodes[i]);
}
}
return offset;};// Determine total offset length from returned offset from rangesvar totalOffsets = function(parentNode, offset) {
if (parentNode.nodeType == 3)
return offset;
if (parentNode.nodeType == 1) {
var total = 0;
// Get child nodes
for (var i=0;i<offset;i++) {
total += calculateNodeOffset(parentNode.childNodes[i]);
}
return total;
}
return 0;};var getNodeAndOffsetAt = function(start, offset) {
var node = start;
var stack = [];
while (true) {
// If arrived
if (offset <= 0)
return { node: node, offset: 0 };
// If will be within current text node
if (node.nodeType == 3 && (offset <= node.nodeValue.length))
return { node: node, offset: Math.min(offset, node.nodeValue.length) };
// Go into children (first one doesn't count)
if (node.firstChild) {
if (node !== start)
offset -= 1;
stack.push(node);
node = node.firstChild;
}
// If can go to next sibling
else if (stack.length > 0 && node.nextSibling) {
// If text, count length
if (node.nodeType === 3)
offset -= node.nodeValue.length + 1;
else
offset -= 1;
node = node.nextSibling;
}
else {
// No children or siblings, move up stack
while (true) {
if (stack.length <= 1) {
// No more options, use current node
if (node.nodeType == 3)
return { node: node, offset: Math.min(offset, node.nodeValue.length) };
else
return { node: node, offset: 0 };
}
var next = stack.pop();
// Go to sibling
if (next.nextSibling) {
// If text, count length
if (node.nodeType === 3)
offset -= node.nodeValue.length + 1;
else
offset -= 1;
node = next.nextSibling;
break;
}
}
}
}};exports.save = function(containerEl) {
// Get range
var selection = window.getSelection();
if (selection.rangeCount > 0) {
var range = selection.getRangeAt(0);
return {
start: getNodeOffset(containerEl, range.startContainer) + totalOffsets(range.startContainer, range.startOffset),
end: getNodeOffset(containerEl, range.endContainer) + totalOffsets(range.endContainer, range.endOffset)
};
}
else
return null;};exports.restore = function(containerEl, savedSel) {
if (!savedSel)
return;
var range = document.createRange();
var startNodeOffset, endNodeOffset;
startNodeOffset = getNodeAndOffsetAt(containerEl, savedSel.start);
endNodeOffset = getNodeAndOffsetAt(containerEl, savedSel.end);
range.setStart(startNodeOffset.node, startNodeOffset.offset);
range.setEnd(endNodeOffset.node, endNodeOffset.offset);
var sel = window.getSelection();
sel.removeAllRanges();
sel.addRange(range);};這僅適用于現代瀏覽器（至少IE 9+）。
