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168 lines
4.7 KiB
Markdown
168 lines
4.7 KiB
Markdown
htmlquery
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====
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[](https://travis-ci.org/antchfx/htmlquery)
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[](https://coveralls.io/github/antchfx/htmlquery?branch=master)
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[](https://godoc.org/github.com/antchfx/htmlquery)
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[](https://goreportcard.com/report/github.com/antchfx/htmlquery)
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Overview
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====
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`htmlquery` is an XPath query package for HTML, lets you extract data or evaluate from HTML documents by an XPath expression.
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`htmlquery` built-in the query object caching feature based on [LRU](https://godoc.org/github.com/golang/groupcache/lru), this feature will caching the recently used XPATH query string. Enable query caching can avoid re-compile XPath expression each query.
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Installation
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====
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```
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go get github.com/antchfx/htmlquery
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```
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Getting Started
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====
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#### Query, returns matched elements or error.
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```go
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nodes, err := htmlquery.QueryAll(doc, "//a")
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if err != nil {
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panic(`not a valid XPath expression.`)
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}
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```
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#### Load HTML document from URL.
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```go
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doc, err := htmlquery.LoadURL("http://example.com/")
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```
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#### Load HTML from document.
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```go
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filePath := "/home/user/sample.html"
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doc, err := htmlquery.LoadDoc(filePath)
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```
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#### Load HTML document from string.
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```go
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s := `<html>....</html>`
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doc, err := htmlquery.Parse(strings.NewReader(s))
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```
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#### Find all A elements.
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```go
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list := htmlquery.Find(doc, "//a")
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```
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#### Find all A elements that have `href` attribute.
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```go
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list := range htmlquery.Find(doc, "//a[@href]")
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```
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#### Find all A elements with `href` attribute and only return `href` value.
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```go
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list := range htmlquery.Find(doc, "//a/@href")
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for n := range list{
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fmt.Println(htmlquery.InnerText(n)) // output @href value without A element.
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}
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```
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### Find the third A element.
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```go
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a := htmlquery.FindOne(doc, "//a[3]")
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```
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#### Evaluate the number of all IMG element.
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```go
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expr, _ := xpath.Compile("count(//img)")
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v := expr.Evaluate(htmlquery.CreateXPathNavigator(doc)).(float64)
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fmt.Printf("total count is %f", v)
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```
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FAQ
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====
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#### `Find()` vs `QueryAll()`, which is better?
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`Find` and `QueryAll` both do the same things, searches all of matched html nodes.
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The `Find` will panics if you give an error XPath query, but `QueryAll` will return an error for you.
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#### Can I save my query expression object for the next query?
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Yes, you can. We offer the `QuerySelector` and `QuerySelectorAll` methods, It will accept your query expression object.
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Cache a query expression object(or reused) will avoid re-compile XPath query expression, improve your query performance.
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#### XPath query object cache performance
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```
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goos: windows
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goarch: amd64
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pkg: github.com/antchfx/htmlquery
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BenchmarkSelectorCache-4 20000000 55.2 ns/op
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BenchmarkDisableSelectorCache-4 500000 3162 ns/op
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```
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#### How to disable caching?
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```
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htmlquery.DisableSelectorCache = true
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```
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Changelogs
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===
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2019-11-19
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- Add built-in query object cache feature, avoid re-compilation for the same query string. [#16](https://github.com/antchfx/htmlquery/issues/16)
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- Added LoadDoc [18](https://github.com/antchfx/htmlquery/pull/18)
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2019-10-05
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- Add new methods that compatible with invalid XPath expression error: `QueryAll` and `Query`.
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- Add `QuerySelector` and `QuerySelectorAll` methods, supported reused your query object.
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2019-02-04
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- [#7](https://github.com/antchfx/htmlquery/issues/7) Removed deprecated `FindEach()` and `FindEachWithBreak()` methods.
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2018-12-28
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- Avoid adding duplicate elements to list for `Find()` method. [#6](https://github.com/antchfx/htmlquery/issues/6)
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Tutorial
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===
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```go
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func main() {
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doc, err := htmlquery.LoadURL("https://www.bing.com/search?q=golang")
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if err != nil {
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panic(err)
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}
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// Find all news item.
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list, err := htmlquery.QueryAll(doc, "//ol/li")
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if err != nil {
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panic(err)
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}
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for i, n := range list {
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a := htmlquery.FindOne(n, "//a")
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fmt.Printf("%d %s(%s)\n", i, htmlquery.InnerText(a), htmlquery.SelectAttr(a, "href"))
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}
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}
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```
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List of supported XPath query packages
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===
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| Name | Description |
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| ------------------------------------------------- | ----------------------------------------- |
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| [htmlquery](https://github.com/antchfx/htmlquery) | XPath query package for the HTML document |
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| [xmlquery](https://github.com/antchfx/xmlquery) | XPath query package for the XML document |
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| [jsonquery](https://github.com/antchfx/jsonquery) | XPath query package for the JSON document |
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Questions
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===
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Please let me know if you have any questions.
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