JS Get Parent Node Method_javascript Tips

How to obtain the elements to be updated is the first problem to be solved. Fortunately, there are many ways to obtain nodes using JavaScript. Here is a brief summary (the following methods have been tested in IE7 and Firefox2.0.0.11):
    1. Obtain through the top-level document node:
(1) document.getElementById(elementId): This method can accurately obtain the required element through the ID of the node, which is a comparison Easy and quick way. If the page contains multiple nodes with the same ID, only the first node will be returned.
Nowadays, there have been many JavaScript libraries such as prototype and Mootools, which provide a simpler method: $(id), and the parameter is still the id of the node. This method can be seen as another way of writing document.getElementById(), but $() is more powerful. For specific usage, please refer to their respective API documents.
             (2) document.getElementsByName(elementName): This method gets the node through the name of the node. As can be seen from the name, this method returns is not a node element, but an array of nodes with the same name. Then, we can loop through a certain attribute of the node to determine whether it is the required node.
For example: In HTML, checkbox and radio both use the same name attribute value to identify elements within a group. If we want to get the selected element now, we first get the shuffled element, and then loop to determine whether the checked attribute value of the node is true.
         (3) document.getElementsByTagName(tagName): This method gets the node through the node’s Tag. This method also returns an array, for example: document. getElementsByTagName('A') will return all hyperlink nodes on the page. Before obtaining the node, the type of the node is generally known, so it is relatively simple to use this method. But the disadvantage is also obvious, that is, the returned array may be very large, which will waste a lot of time. So, is this method useless? Of course not. This method is different from the two above. It is not a proprietary method of the document node and can also be applied to other nodes, which will be mentioned below.
2. Get through the parent node:
(1) parentObj.firstChild: If the node is the first of the known node (parentObj) This method can be used for child nodes. This attribute can be used recursively, that is, it supports the form of parentObj.firstChild.firstChild.firstChild..., so that deeper nodes can be obtained.
       (2) parentObj.lastChild: Obviously, this attribute is to get the last child node of the known node (parentObj). Like firstChild, it can also be used recursively.
In use, if we combine the two, we will achieve a more exciting effect, namely: parentObj.firstChild.lastChild.lastChild...
(3) parentObj.childNodes: Get the child node array of a known node, and then find the required node through looping or indexing.
                                                                                                                            The child nodes of the node.          (4)
parentObj.children: Get the direct child node array of the known node.    Note
: After testing, it has the same effect as childNodes on IE7, but Firefox2.0.0.11 does not support it. This is why I use a different style than other methods.Therefore its use is not recommended.
       (5) parentObj.getElementsByTagName(tagName): The usage method will not be described in detail. It returns an array of child nodes of the specified value among all child nodes of the known node. For example: parentObj.getElementsByTagName('A') returns all hyperlinks in known child nodes.
3. Obtain through adjacent nodes:
(1) neighbourNode.previousSibling: Get the previous node of the known node (neighbourNode), This property, like the previous firstChild and lastChild, seems to be usable recursively.
(2) neighbourNode.nextSibling: Get the next node of the known node (neighbourNode), also supports recursion.
4. Obtain through child nodes:
(1) childNode.parentNode: Get the parent node of a known node.

The methods mentioned above are just some basic methods. If you use JavaScript libraries such as Prototype, you may also get other different methods, such as obtaining through the class of the node, etc. However, if you can flexibly use the various methods above, I believe you should be able to handle most programs