javascript getElementsByTagName_javascript技巧

Copy code The code is as follows:

function getElementsByTagName(node, tagName) {
var elements = [ ], i = 0, anyTag = tagName === "*", next = node.firstChild;
while ((node ​​= next)) {
if (anyTag ? node.nodeType === 1 : node .nodeName === tagName) elements[i ] = node;
next = node.firstChild || node.nextSibling;
while (!next && (node ​​= node.parentNode)) next = node.nextSibling;
}
return elements; gather.
Syntax
document.getElementsByTagName(tagname)

Description
The getElementsByTagName() method returns elements in the order they are in the document. If you pass the special string "*" to the getElementsByTagName() method, it will return a list of all elements in the document, and the order in which the elements are arranged is the order they are in the document.
Tips and Notes Note: The string passed to the getElementsByTagName() method can be case-insensitive.
Example
Example 1




Copy code


The code is as follows:

< ;input name="myInput" type="text" size="20" />



value="How many input elements?" />




Example 2
can be used The getElementsByTagName() method gets a list of HTML elements of any type. For example, the following code can get all tables in the document:

Copy the code


The code is as follows:

var tables = document.getElementsByTagName("table"); alert ("This document contains " tables.length " tables"); Example 3

If you know the document very well structure, you can also use the getElementsByTagName() method to get a specific element in the document. For example, the following code can get the fourth paragraph in the document:

var myParagragh = document.getElementsByTagName("p")[3];
However, we still think that if you need to operate on a specific element, it is more efficient to use the getElementById() method.