DOM4 compareDocumentPosition
我想实现compareDocumentPosition. Resig已经取得了great start at doing just this.我已经把他的代码整理好了
function compareDocumentPosition(other) {
var ret = 0;
if (this.contains) {
if (this !== other && this.contains(other)) {
ret += 16;
}
if (this !== other && other.contains(this)) {
ret += 8;
}
if (this.sourceIndex >= 0 && other.sourceIndex >= 0) {
if (this.sourceIndex < other.sourceIndex) {
ret += 4;
}
if (this.sourceIndex > other.sourceIndex) {
ret += 2;
}
} else {
ret += 1;
}
}
return ret;
}
这适用于Element,但不适用于Text或DocumentFragment.这是因为IE8不会在这些节点上提供.sourceIndex. (它不会给.contains,但我已经解决了这个问题)
如何有效地写入对应于DOCUMENT_POSITION_FOLLOWING和DOCUMENT_POSITION_PRECEDING的= 4和= 2位.
为了额外的参考,这两个是由DOM4定义的树顺序定义的
An object A is preceding an object B if A and B are in the same tree and A comes before B in tree order.
An object A is following an object B if A and B are in the same tree and A comes after B in tree order.
The tree order is preorder,depth-first traversal.
大多数现代浏览器都实现了这一点(包括IE9).所以你只需要在IE8中运行的东西(我不关心IE6 / 7,但它是否真的很棒！)
解决方法
function recursivelyWalk(nodes,cb) {
for (var i = 0,len = nodes.length; i < len; i++) {
var node = nodes[i];
var ret = cb(node);
if (ret) {
return ret;
}
if (node.childNodes && node.childNodes.length) {
var ret = recursivelyWalk(node.childNodes,cb);
if (ret) {
return ret;
}
}
}
}
function testNodeForComparePosition(node,other) {
if (node === other) {
return true;
}
}
function compareDocumentPosition(other) {
function identifyWhichIsFirst(node) {
if (node === other) {
return "other";
} else if (node === reference) {
return "reference";
}
}
var reference = this,referenceTop = this,otherTop = other;
if (this === other) {
return 0;
}
while (referenceTop.parentNode) {
referenceTop = referenceTop.parentNode;
}
while (otherTop.parentNode) {
otherTop = otherTop.parentNode;
}
if (referenceTop !== otherTop) {
return Node.DOCUMENT_POSITION_DISCONNECTED;
}
var children = reference.childNodes;
var ret = recursivelyWalk(
children,testNodeForComparePosition.bind(null,other)
);
if (ret) {
return Node.DOCUMENT_POSITION_CONTAINED_BY +
Node.DOCUMENT_POSITION_FOLLOWING;
}
var children = other.childNodes;
var ret = recursivelyWalk(
children,reference)
);
if (ret) {
return Node.DOCUMENT_POSITION_CONTAINS +
Node.DOCUMENT_POSITION_PRECEDING;
}
var ret = recursivelyWalk(
[referenceTop],identifyWhichIsFirst
);
if (ret === "other") {
return Node.DOCUMENT_POSITION_PRECEDING;
} else {
return Node.DOCUMENT_POSITION_FOLLOWING;
}
}
