This article brings you relevant knowledge about javascript. It mainly introduces issues related to DOM attribute members and document flow. It divides the form from top to bottom into rows and rows, and Arranging elements in each row from left to right is the document flow. Let's take a look at it. I hope it will be helpful to everyone.
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Divide the form into rows from top to bottom, and arrange the elements in each row from left to right, which is the normal flow/document flow.
The reading and output order of documents, which is the form of reading and outputting from left to right and top to bottom that we usually see.
The situation of breaking away from the document flow:
1. float float
The float will break away from the document flow but not the text flow. In other box models The text will still make way for it, > wrap around it
2. Position: absolute/fixed Absolute positioning
Absolute positioning will make the element break away from the document flow and the text flow. Other box model elements and the arrangement of text in them will ignore it
Document flow and text flow can be understood as positioning/position
JavaScript operates web pages Interface, the full name is "Document Object Model" (Document Object Model).
There are several concepts: document, element, node
The entire document is a document node
Each tag is an element node
Contained in The text in the element is a text node
Each attribute is an attribute node
Comments belong to comment nodes
DOM tree is a structure
The so-called hierarchical structure refers to the relationship between elements
Father, son, brother
The tree output by the parser is composed of DOM elements and attribute nodes
When we say that the tree contains DOM nodes, it means that the tree is composed of elements that implement the DOM interface. These implementations include other properties required internally by browsers.
The hierarchical structure relationship remains unchanged after leaving the document flow
The attributes are nodes (HTML elements ) value, you can get or set it.
Programming interface
The HTML DOM can be accessed through JavaScript (and other programming languages).
All HTML elements are defined as objects, and the programming interface is object methods and object properties.
Methods are actions you can perform (such as adding or modifying elements).
Attributes are values that you can get or set (such as the name or content of a node).
innerHTML property
The easiest way to get the content of an element is to use the innerHTML property.
The innerHTML attribute is useful for getting or replacing the content of an HTML element.
Example
The following code obtains the innerHTML of the
element with id="intro":
<html>
<body>
<p id="intro">Hello World!</p>
<script>
var txt=document.getElementById("intro").innerHTML;
document.write(txt);
</script>
</body>
</html>Output result:
In the above example, getElementById is a method and innerHTML is a property.
The innerHTML attribute can be used to get or change any HTML element, including and
.nodeName attribute
The nodeName attribute specifies the name of the node.
nodeName is read-only
The nodeName of the element node is the same as the label name
The nodeName of the attribute node is the same as the attribute name The same
The nodeName of the text node is always #text
The nodeName of the document node is always #document
Note: nodeName always contains the uppercase tag name of the HTML element.
nodeValue attribute
The nodeValue attribute specifies the value of the node.
The nodeValue of the element node is undefined or null
The nodeValue of the text node is the text itself
The nodeValue of the attribute node is the attribute value
Get the value of the element
The following example will retrieve
Text node value of label:
Instance
<html>
<body>
<p id="intro">Hello World!</p>
<script type="text/javascript">
x=document.getElementById("intro");
document.write(x.firstChild.nodeValue);
</script>
</body>
</html>Output result:
##nodeType attribute
nodeType property returns the type of node. nodeType is read-only. The more important node types are:
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