About node content enhancement in javascript_Basic knowledge

1. Element node

Copy code The code is as follows:

//Test element node, output node name, node type, node value
var liElements=document.getElementsByTagName("li");
for(var i=0;i alert(liElements[i].nodeName);
alert(liElements[i].nodeType);
alert(liElements[i].nodeValue);
}

2. Attribute node

Copy code The code is as follows:

[/c//Test attribute node, output attribute node name, node type, node value
var liElements=document.getElementsByTagName("li");
for(var i=0;i var attrElement=liElements[i].getAttributeNode("value")
alert("attrElement.nodeName " attrElement.nodeName);
alert("attrElement.nodeType " attrElement. nodeType);
alert("attrElement.nodeValue " liElements[i].getAttribute("value"));
}ode]

3. Text node
[code]
//Test element node, output node name, node type, node value
var liElements=document.getElementsByTagName(" li");
for(var i=0;i alert(liElements[i].childNodes[0].nodeName);
alert(liElements[i] .childNodes[0].nodeType);
alert(liElements[i].childNodes[0].nodeValue);

liElements[i].childNodes[0].nodeValue="Nanjing";
alert(liElements[i].childNodes[0].nodeValue);

//Another way to read Method
alert(liElements[i].firstChild.nodeName);
alert(liElements[i].firstChild.nodeType);
alert(liElements[i].firstChild.nodeValue);
}

4. Replace node

replaceChild()
Replaces a child node in a given parent element with another child node
var reference = element.replaceChild(newChild,oldChild);
The return value is a pointer to the The reference pointer of the child node being replaced.
If the inserted child node also has child nodes, those child nodes are also inserted into the target node

Copy code The code is as follows:

//Method 1
// var cityElement= document.getElementById("city");
// var loveElement=document.getElementById("love");
// var cityChildElement=document.getElementById("beijing");
// var loveChildElement =document.getElementById("fankong");
// var oldElement=cityElement.replaceChild(loveChildElement,cityChildElement);
// loveElement.appendChild(oldElement);
// alert(oldElement.getAttribute( "id"));

var cityElement=document.getElementById("city");
var cityElement.onclick=function(){
var cityChildElement=document.getElementById("beijing");
var loveChildElement=document.getElement ById ("fankong");
var oldElement=cityElement.replaceChild(loveChildElement,cityChildElement);
loveElement.appendChild(oldElement);
alert(oldElement.getAttribute("id"));
}

5. Find attribute nodes

getAttribute()
Returns the value of a given attribute node for a given element
var attributeValue = element.getAttribute(attributeName);
The name of the given attribute must be passed in the form of a string Give the method.
The value of the given attribute will be returned in the form of a string. If the given attribute does not exist, getAttribute() will return an empty string.
Get the attribute node through the attribute
getAttributeNode (name of the attribute) --Node

Beijing

//Get the value of the attribute through the attribute name
var bjElement=document. getElementById("bj");
var attributeValue=eduElement.getAttribute("name");
alert("attributeValue " attributeValue);

//Get the node of the attribute through the attribute name
var bjNode=eduElement.getAttributeNode("name");
alert(eduNode.nodeValue);
alert(eduNode.nodeType);
alert(eduNode.nodeName);

6. Set attribute nodes

setAttribute()
Adds a new attribute value to a given element node or changes the value of its existing attribute.
element.setAttribute(attributeName,attributeValue);
The name and value of the attribute must be passed to this method in the form of a string
If this attribute already exists, its value will be refreshed;
If If it does not exist, the setAttribute() method will first create it and then assign a value to it.

Beijing

//Get the reference of the element
var bjElement=document.getElementById("bj");
//Set the attribute value
bjElement.setAttribute("name","beijing");
//Get the set attribute value
var nameValue=bjElement.getAttribute("name");
alert("nameValue " nameValue);

7. Create new element nodes

createElement()
Creates a new element node according to the given tag name. The method has only one parameter: the name of the element to be created, which is a string.
var reference = document.createElement(element); The return value of the
method: is a reference pointer pointing to the newly created node. The return value is an element node, so its nodeType attribute value is equal to 1.
New element nodes will not be automatically added to the document. The new node has no nodeParent attribute. It is just an object that exists in the JavaScript context.
var pElement = document.createElement("p");

//Create a new element
var pElement=document.createElement("li");
//Set attribute value
pElement.setAttribute("id","pid");

//Get the parent element
var loveElement=document.getElementById("love");
//Add child elements to the parent element
loveElement.appendChild(pElement);

//Get the newly created element by id
var pidElement=document.getElementById("pid");
alert(pidElement.getAttribute("id"));

8. Create a new text node

createTextNode()
Creates a new text node containing the given text. The return value of this method is a reference pointer to the new text node.
var textNode = document.createTextNode(text); The
method has only one parameter: the text string contained in the new text node. The return value of the
method: is a reference pointer pointing to the new node. It is a text node, so its nodeType attribute is equal to 3.
New element nodes will not be automatically added to the document, and new nodes have no nodeParent attribute

var pElementText=document.createElement("li") ;
var textElement=document.createTextNode("Nanjing");
pElementText.appendChild(textElement);

9. Insert node (1)

appendChild()
Add a child node to the given element:                                                                                                        the last child node of element . The return value of the
method is a reference pointer to the newly added child node.
This method is usually used in conjunction with createElement() createTextNode()
New nodes can be appended to any element in the document

Copy code The code is as follows:

var newliElement=document.createElement("li");
var textNode=document.createTextNode("Beijing");
newliElement.appendChild(textNode);
document.body. appendChild(newliElement);

var liElement=document.getElementsByTagName("li");
var textValue=liElement[0].firstChild.nodeValue;
alert(textValue);

10. Delete node

removeChild()
Removes a child node from a given element
var reference = element.removeChild(node);
The return value is a reference pointer to the deleted child node.
When a node is deleted by the removeChild() method, all child nodes contained in this node will be deleted at the same time.

Copy code The code is as follows:

< li value="beijing^" id="beijing">Beijing

var ulElement=document.getElementById("city");
var liElement=document.getElementById( "beijing");
ulElement.removeChild(liElement);

If you want to delete a node but don’t know which parent node it is, the parentNode attribute can help.

Copy code The code is as follows:

< li value="beijing^" id="beijing">Beijing

var liElement=document.getElementById("beijing");
var parentElement=liElement.parentNode;
parentElement.removeChild(liElement);

11. Traverse the node tree

ChildNodes: Returns an array consisting of the child nodes of a given element node:
var nodeList = node.childNodes;
Neither text nodes nor attribute nodes can contain any more child nodes, so they The ChildNodes property will always return an empty array.
If you want to know whether an element has child nodes, you can use the hasChildNodes method.
If you want to know how many child nodes a certain element has, you can use the length property of the childNodes array.
The childNodes attribute is a read-only attribute.

12. Get the first child node

firstChild: This attribute returns the first child node of a given element node and returns the pointer of this node object.
var reference = node.firstChild;
Neither text nodes nor attribute nodes may contain any child nodes, so their firstChild property will always return null.
The firstChild attribute of an element is equivalent to the first node in the childNodes node collection of this element, that is:
var reference = node.ChildNodes[0];
The firstChild attribute is a read-only attribute .

13. Get the last child node

lastChild: an attribute corresponding to firstChild.
nextSibling: Returns the next sibling node of a given node.
parentNode: Returns the parent node of a given node.
The node returned by the parentNode attribute is always an element node, because only element nodes may contain child nodes.
The document node has no parent node.
previousSibling: Returns the previous sibling node of a given node

14. innerHTML attribute

Almost all browsers support this attribute, but it is not part of the DOM standard.
The innerHTML attribute can be used to read and write the HTML content within a given element.

Copy code The code is as follows:

< /div>
var divElement=document.getElementById("city");
divElement.innerHTML="

Beijing

" ;