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README.md	updated dependencies	2022-03-26 12:13:52 +01:00

README.md

htmlquery

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.

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)

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

Changelogs

2019-11-19

Add built-in query object cache feature, avoid re-compilation for the same query string. #16
Added LoadDoc 18

2019-10-05

Add new methods that compatible with invalid XPath expression error: QueryAll and Query.
Add QuerySelector and QuerySelectorAll methods, supported reused your query object.

2019-02-04

#7 Removed deprecated FindEach() and FindEachWithBreak() methods.

2018-12-28

Avoid adding duplicate elements to list for Find() method. #6

Tutorial

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")
		fmt.Printf("%d %s(%s)\n", i, htmlquery.InnerText(a), htmlquery.SelectAttr(a, "href"))
	}
}

List of supported XPath query packages

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

Questions

Please let me know if you have any questions.