DOM and XPATH

发布时间：2023年12月26日

DOM

  • Originally developed for HTML. Supported by most browsers.

  • Represents the content of the XML or HTML document as a tree structure.

  • Using DOM, we can easily read and update the contents of the document.

D: Document —> file

O: Object —> tags elements

M: Model —> layout structure

Online DOM viewer:

Live DOM Viewer

XPATH

  • Allows us to use path expressions to navigate an XML document.

  • It allow us to select only the nodes we're interested in.

its :

  • Expression language.

  • Contains some standard functions.

  • Non-XML

XPATH works on the following kinds of nodes:

ExpressionDescription
nodenameSelects all nodes with the name"nodename"
/Selects from the root node
//Selects nodes in the document from the current node that match the selection no matter where they are
.Selects the value of the current node
..Selects the parent of the current node
@Selects attributes

Predicates

  • similar to filters

  • They always appear in[]

  • They appear after the axis and node text

Path ExpressionResult
/bookstore/book[1]Selects the first book element that is the child of the bookstore element.
/bookstore/book[last()]Selects the last book element that is the child of the bookstore element
/bookstore/book[last()-1]Selects the last but one book element that is the child of the bookstore element
/bookstore/book[position()<3]Selects the first two book elements that are children of the bookstore element
//title[@lang]Selects all the title elements that have an attribute named lang
//title[@lang='en']Selects all the title elements that have a "lang" attribute with a value of "en"
/bookstore/book[price>35.00]Selects all the book elements of the bookstore element that have a price element
/bookstore/book[price>35.00]/titleSelects all the title elements of the book elements of the bookstore element that have a price element with a value greater than 35.00

XPATH Axes

an Axes represents a relationship to the current node on the tree.

AxisNameResult
ancestorSelects all ancestors (parent, grandparent, etc.) of the current node
ancestor-or-selfSelects all ancestors (parent, grandparent, etc.) of the current node and the current node itself
attributeSelects all attributes of the current node
childSelects all children of the current node
descendantSelects all descendants (children, grandchildren, etc.) of the current node
descendant-or-selfSelects all descendants (children, grandchildren, etc.) of the current node and the current node itself
followingSelects everything in the document after the closing tag of the current node
following-siblingSelects all siblings after the current node
namespaceSelects all namespace nodes of the current node
parentSelects the parent of the current node
precedingSelects all nodes that appear before the current node in the document, except ancestors, attribute nodes and namespace nodes
preceding-siblingSelects all siblings before the current node
selfSelects the current node
文章来源:https://blog.csdn.net/weixin_74783792/article/details/135220370
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