About javascript document.createDocumentFragment()_javascript tips-JS Tutorial-php.cn

About javascript document.createDocumentFragment()_javascript tips

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Release： 2016-05-16 18:54:35

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It supports the following DOM2 methods:
appendChild, cloneNode, hasAttributes, hasChildNodes, insertBefore, normalize, removeChild, replaceChild.
also supports the following DOM2 attributes:
attributes, childNodes, firstChild, lastChild, localName, namespaceURI, nextSibling , nodeName, nodeType, nodeValue, ownerDocument, parentNode, prefix, previousSibling, textContent.
Other methods can use documentFragment as a parameter (such as Node's appendChild and insertBefore methods), so that the fragment can be appended to the parent object .
Example:

Copy code The code is as follows:

var frag = document.createDocumentFragment( ); 
frag.appendChild(document.createTextNode('Ipsum Lorem')); 
document.body.appendChild(frag); 

document.createDocumentFragment() To put it bluntly, Use DOM sparingly. Every JavaScript operation on the DOM will change the rendering of the page and re-refresh the entire page, which consumes a lot of time. To solve this problem, you can create a document fragment, attach all new nodes to it, and then add the contents of the document fragment to the document at once.

Copy code The code is as follows:

var oui=document.getElementById("oItem"); 
for(var i=0;i<10;i ) 
{ 
var oli=document.createElement("li"); 
oui.appendChild(oli); 
oli. appendChild(document.createTextNode("Item" i)); 
} 

The above code calls oui.appendChild(oli) in the loop. After each execution of this statement, browse The server will update the page. Secondly, oui.appendChild() below adds text nodes and also updates the page. So the page needs to be updated 20 times in total.
In order to optimize the page, we need to minimize DOM operations, add list items after adding text nodes, and use creatDocumentFragment() reasonably. The code is as follows:

Copy code The code is as follows:

var oui=document.getElementById("oItem"); 
var oFragment=document.createDocumentFragment(); 
for(var i=0;i<10;i ){ 
var oli=document.createElement("li"); 
oli.appendChild(document.createTextNode("Item" i)); 
oFragment.appendChild(oli); 
} 
oui.appendChild(oFragment); 

W3C reference: http://www.w3.org/TR/DOM- Level-2-Core/core.html#ID-B63ED1A3
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DocumentFragment is a "lightweight" or "minimal" Document object. It is very common to want to be able to extract a portion of a document's tree or to create a new fragment of a document. Imagine implementing a user command like cut or rearranging a document by moving fragments around. It is desirable to have an object which can hold such fragments and it is quite natural to use a Node for this purpose. While it is true that a Document object could fulfill this role, a Document object can potentially be a heavyweight object, depending on the underlying implementation. What is really needed for this is a very lightweight object. DocumentFragment is such an object.

Furthermore, various operations -- such as inserting nodes as children of another Node -- may take DocumentFragment objects as arguments; this results in all the child nodes of the DocumentFragment being moved to the child list of this node.

The children of a DocumentFragment node are zero or more nodes representing the tops of any sub-trees defining the structure of the document. DocumentFragment nodes do not need to be well-formed XML documents (although they do need to follow the rules imposed upon well-formed XML parsed entities, which can have multiple top nodes). For example, a DocumentFragment might have only one child and that child node could be a Text node. Such a structure model represents neither an HTML document nor a well-formed XML document.

When a DocumentFragment is inserted into a Document (or indeed any other Node that may take children) the children of the DocumentFragment and not the DocumentFragment itself are inserted into the Node. This makes the DocumentFragment very useful when the user wishes to create nodes that are siblings; the DocumentFragment acts as the parent of these nodes so that the user can use the standard methods from the Node interface, such as insertBefore and appendChild.