问题
DOM4 compareDocumentPosition
I want to implement compareDocumentPosition. Resig has made a great start at doing just this. I've taken his code and neatened it up
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;
}
This works for Element
but does not for Text
or DocumentFragment
. This is because IE8 does not give .sourceIndex
on those nodes. (It doesn't give .contains
either but I've fixed that problem already)
How do I efficiently write the +=4
and +=2
bit which correspond to DOCUMENT_POSITION_FOLLOWING and DOCUMENT_POSITION_PRECEDING.
For extra reference those two are defined by tree-order which DOM4 defines as
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.
Most modern browsers implement this (including IE9). So you only need something that works in IE8 (I don't care about IE6/7, but if it works awesome!)
回答1:
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,
testNodeForComparePosition.bind(null, 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;
}
}
I wrote it myself. I thought this implementation was bugged but it was a bug in some other code of mine. Seems pretty solid.
回答2:
The answer from Raynos is a top start, but is not runnable out of the box. Node.*
cannot be found and .bind
is not available in IE8.
Here is the code ready for use in Internet Explorer 8:
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;
}
}
var DOCUMENT_POSITION_DISCONNECTED = 1;
var DOCUMENT_POSITION_PRECEDING = 2;
var DOCUMENT_POSITION_FOLLOWING = 4;
var DOCUMENT_POSITION_CONTAINS = 8;
var DOCUMENT_POSITION_CONTAINED_BY = 16;
function compareDocumentPosition(thisNode, other) {
function identifyWhichIsFirst(node) {
if (node === other) {
return "other";
} else if (node === reference) {
return "reference";
}
}
var reference = thisNode,
referenceTop = thisNode,
otherTop = other;
if (this === other) {
return 0;
}
while (referenceTop.parentNode) {
referenceTop = referenceTop.parentNode;
}
while (otherTop.parentNode) {
otherTop = otherTop.parentNode;
}
if (referenceTop !== otherTop) {
return DOCUMENT_POSITION_DISCONNECTED;
}
var children = reference.childNodes;
var ret = recursivelyWalk(
children,
function(p) {
(function() {
var localOther = other;
return testNodeForComparePosition(localOther, p);
})();
}
);
if (ret) {
return DOCUMENT_POSITION_CONTAINED_BY +
DOCUMENT_POSITION_FOLLOWING;
}
var children = other.childNodes;
var ret = recursivelyWalk(
children,
function(p) {
(function() {
var localOther = reference;
return testNodeForComparePosition(localOther, p);
})();
}
);
if (ret) {
return DOCUMENT_POSITION_CONTAINS +
DOCUMENT_POSITION_PRECEDING;
}
var ret = recursivelyWalk(
[referenceTop],
identifyWhichIsFirst
);
if (ret === "other") {
return DOCUMENT_POSITION_PRECEDING;
} else {
return DOCUMENT_POSITION_FOLLOWING;
}
}
You call it like this:
compareDocumentPosition(sourceElement, elementToTest)
(It's like calling sourceElement.compareDocumentPosition(elementToTest)
)
来源:https://stackoverflow.com/questions/8334286/cross-browser-compare-document-position