JavaScript iterates through HTML form elements and form definitions

Source: Internet
Author: User

The following JavaScript code, through the Document object, iterates through all the HTML elements (HTML DOM element).

<meta http-equiv="Content-type" Content="text/html; Charset=utf-8 "><head><script> //Display all HTML elements that have an "ID" attribute  function displayallelem(){var   Elems = document.getElementsByTagName ("*");  for (var i=0; i<elems.length;i++) { If (Elems[i].hasattribute ("id")) {tmp = elems[i].id + ", FieldType =" + elem     S[i].getattribute ("FieldType") + "element type =" + elems[i].nodename;     Alert (TMP); }   }    }   </script></head><body><H1>Form element Traversal Test JavaScript</H1><p id="Demo" fieldtype="Test">This is a paragraph.</P><div> <input id="name" fieldtype="char">Name</input><br>Define the data type by customizing the property "FieldType".<br><input id="old" fieldtype="number" value ="> "Age</input><br><button id="Test" type="button" onclick=" Displayallelem () ">Display Element</button></div> </body></html>

Note: Code explanation
(1). Hasattribute ("id"), determine if there is an "id" attribute, if the specified attribute exists, then the Hasattribute () method returns True, otherwise returns false;
(2). ID, return the ID of the element;
(3). getattribute ("FieldType"), returns the value of the specified attribute for the element node.

From the above code, think:

    • When defining a form, the key information of the form data item, such as the data type, is defined directly by the attributes of the element.
    • By iterating through the form, getting the form design definition, and its business data values, convert the two directly to the Bson type store in high MongoDB;
    • When displaying or editing, the form design is defined as a template, and the data content is written back.

The following information is provided for reference W3school.

HTML DOM Document Object

Document Object
Each HTML document that is loaded into the browser becomes the document object.
The Document object allows us to access all elements of an HTML page from within a script.
Tip: The Document object is part of the Window object and can be accessed through the Window.document property.

HTML DOM getElementsByTagName () method
    • Definition and usage
getElementsByTagName() 方法可返回带有指定标签名的对象的集合。
    • Grammar
document.getElementsByTagName(tagname)
    • Description

The getElementsByTagName () method returns elements in the order that they are in the document.
If you pass the special string "*" to the getElementsByTagName () method, it returns a list of all the elements in the document, the order in which they are arranged in the document.

HTML DOM Element object HTML DOM node

In the HTML DOM (Document Object model), each part is a node:

    • The document itself is a document node
    • All HTML elements are element nodes
    • All HTML attributes are attribute nodes
    • Text within an HTML element is a text node
    • Comment is a comment node

Element Object

    • In the HTML DOM, the element object represents an HTML element.
    • The element object can have child nodes of the type elements node, the text node, and the annotation node.
    • The NodeList object represents a list of nodes, such as a collection of child nodes of an HTML element.
    • Elements can also have properties. property is an attribute node
HTML DOM NodeType Properties

For each node type, the return value of the NodeName and NodeValue properties:

Serial Number node Type nodename return NodeValue return
1 Element Element name Null
2 Attr Property name Property value
3 Text Text The contents of the node
4 Cdatasection Cdata-section The contents of the node
5 EntityReference Entity reference name Null
6 Entity Entity Name Null
7 ProcessingInstruction Target The contents of the node
8 Comment Comment Comment Text
9 Document Document Null
10 DocumentType Document type name Null
11 DocumentFragment Document fragment Null
12 Notation Symbol name Null

Reference:
W3school provides content: http://www.w3school.com.cn/jsref/dom_obj_document.asp

JavaScript iterates through HTML form elements and form definitions

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