htmlquery

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Published: Jan 26, 2023 License: MIT Imports: 11 Imported by: 566

README

htmlquery

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Overview

htmlquery is an XPath query package for HTML, lets you extract data or evaluate from HTML documents by an XPath expression.

htmlquery built-in the query object caching feature based on LRU, this feature will caching the recently used XPATH query string. Enable query caching can avoid re-compile XPath expression each query.

You can visit this page to learn about the supported XPath(1.0/2.0) syntax. https://github.com/antchfx/xpath

XPath query packages for Go

Name Description
htmlquery XPath query package for the HTML document
xmlquery XPath query package for the XML document
jsonquery XPath query package for the JSON document

Installation

go get github.com/antchfx/htmlquery

Getting Started

Query, returns matched elements or error.
nodes, err := htmlquery.QueryAll(doc, "//a")
if err != nil {
	panic(`not a valid XPath expression.`)
}
Load HTML document from URL.
doc, err := htmlquery.LoadURL("http://example.com/")
Load HTML from document.
filePath := "/home/user/sample.html"
doc, err := htmlquery.LoadDoc(filePath)
Load HTML document from string.
s := `<html>....</html>`
doc, err := htmlquery.Parse(strings.NewReader(s))
Find all A elements.
list := htmlquery.Find(doc, "//a")
Find all A elements that have href attribute.
list := htmlquery.Find(doc, "//a[@href]")	
Find all A elements with href attribute and only return href value.
list := htmlquery.Find(doc, "//a/@href")	
for _ , n := range list{
	fmt.Println(htmlquery.SelectAttr(n, "href")) // output @href value
}
Find the third A element.
a := htmlquery.FindOne(doc, "//a[3]")
Find children element (img) under A href and print the source
a := htmlquery.FindOne(doc, "//a")
img := htmlquery.FindOne(a, "//img")
fmt.Prinln(htmlquery.SelectAttr(img, "src")) // output @src value
Evaluate the number of all IMG element.
expr, _ := xpath.Compile("count(//img)")
v := expr.Evaluate(htmlquery.CreateXPathNavigator(doc)).(float64)
fmt.Printf("total count is %f", v)

Quick Starts

func main() {
	doc, err := htmlquery.LoadURL("https://www.bing.com/search?q=golang")
	if err != nil {
		panic(err)
	}
	// Find all news item.
	list, err := htmlquery.QueryAll(doc, "//ol/li")
	if err != nil {
		panic(err)
	}
	for i, n := range list {
		a := htmlquery.FindOne(n, "//a")
		if a != nil {
		    fmt.Printf("%d %s(%s)\n", i, htmlquery.InnerText(a), htmlquery.SelectAttr(a, "href"))
		}
	}
}

FAQ

Find() vs QueryAll(), which is better?

Find and QueryAll both do the same things, searches all of matched html nodes. The Find will panics if you give an error XPath query, but QueryAll will return an error for you.

Can I save my query expression object for the next query?

Yes, you can. We offer the QuerySelector and QuerySelectorAll methods, It will accept your query expression object.

Cache a query expression object(or reused) will avoid re-compile XPath query expression, improve your query performance.

XPath query object cache performance
goos: windows
goarch: amd64
pkg: github.com/antchfx/htmlquery
BenchmarkSelectorCache-4                20000000                55.2 ns/op
BenchmarkDisableSelectorCache-4           500000              3162 ns/op
How to disable caching?
htmlquery.DisableSelectorCache = true

Questions

Please let me know if you have any questions.

Documentation

Overview

Package htmlquery provides extract data from HTML documents using XPath expression.

Index

Constants

This section is empty.

Variables

View Source
var DisableSelectorCache = false

DisableSelectorCache will disable caching for the query selector if value is true.

View Source
var SelectorCacheMaxEntries = 50

SelectorCacheMaxEntries allows how many selector object can be caching. Default is 50. Will disable caching if SelectorCacheMaxEntries <= 0.

Functions

func ExistsAttr added in v1.2.4

func ExistsAttr(n *html.Node, name string) bool

ExistsAttr returns whether attribute with specified name exists.

func Find

func Find(top *html.Node, expr string) []*html.Node

Find is like QueryAll but Will panics if the expression `expr` cannot be parsed.

See `QueryAll()` function.

func FindOne

func FindOne(top *html.Node, expr string) *html.Node

FindOne is like Query but will panics if the expression `expr` cannot be parsed. See `Query()` function.

func InnerText

func InnerText(n *html.Node) string

InnerText returns the text between the start and end tags of the object.

func LoadDoc added in v1.2.0

func LoadDoc(path string) (*html.Node, error)

LoadDoc loads the HTML document from the specified file path.

func LoadURL

func LoadURL(url string) (*html.Node, error)

LoadURL loads the HTML document from the specified URL.

func OutputHTML

func OutputHTML(n *html.Node, self bool) string

OutputHTML returns the text including tags name.

func Parse

func Parse(r io.Reader) (*html.Node, error)

Parse returns the parse tree for the HTML from the given Reader.

func Query added in v1.1.0

func Query(top *html.Node, expr string) (*html.Node, error)

Query runs the given XPath expression against the given html.Node and returns the first matching html.Node, or nil if no matches are found.

Returns an error if the expression `expr` cannot be parsed.

func QueryAll added in v1.1.0

func QueryAll(top *html.Node, expr string) ([]*html.Node, error)

QueryAll searches the html.Node that matches by the specified XPath expr. Return an error if the expression `expr` cannot be parsed.

func QuerySelector added in v1.1.0

func QuerySelector(top *html.Node, selector *xpath.Expr) *html.Node

QuerySelector returns the first matched html.Node by the specified XPath selector.

func QuerySelectorAll added in v1.1.0

func QuerySelectorAll(top *html.Node, selector *xpath.Expr) []*html.Node

QuerySelectorAll searches all of the html.Node that matches the specified XPath selectors.

func SelectAttr

func SelectAttr(n *html.Node, name string) (val string)

SelectAttr returns the attribute value with the specified name.

Types

type NodeNavigator

type NodeNavigator struct {
	// contains filtered or unexported fields
}

func CreateXPathNavigator

func CreateXPathNavigator(top *html.Node) *NodeNavigator

CreateXPathNavigator creates a new xpath.NodeNavigator for the specified html.Node.

func (*NodeNavigator) Copy

func (h *NodeNavigator) Copy() xpath.NodeNavigator

func (*NodeNavigator) Current

func (h *NodeNavigator) Current() *html.Node

func (*NodeNavigator) LocalName

func (h *NodeNavigator) LocalName() string

func (*NodeNavigator) MoveTo

func (h *NodeNavigator) MoveTo(other xpath.NodeNavigator) bool

func (*NodeNavigator) MoveToChild

func (h *NodeNavigator) MoveToChild() bool

func (*NodeNavigator) MoveToFirst

func (h *NodeNavigator) MoveToFirst() bool

func (*NodeNavigator) MoveToNext

func (h *NodeNavigator) MoveToNext() bool

func (*NodeNavigator) MoveToNextAttribute

func (h *NodeNavigator) MoveToNextAttribute() bool

func (*NodeNavigator) MoveToParent

func (h *NodeNavigator) MoveToParent() bool

func (*NodeNavigator) MoveToPrevious

func (h *NodeNavigator) MoveToPrevious() bool

func (*NodeNavigator) MoveToRoot

func (h *NodeNavigator) MoveToRoot()

func (*NodeNavigator) NodeType

func (h *NodeNavigator) NodeType() xpath.NodeType

func (*NodeNavigator) Prefix

func (*NodeNavigator) Prefix() string

func (*NodeNavigator) String

func (h *NodeNavigator) String() string

func (*NodeNavigator) Value

func (h *NodeNavigator) Value() string

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