cascadia

The Cascadia package implements CSS selectors for use with the parse trees produced by the html package.

To test CSS selectors without writing Go code, check out cascadia the command line tool, a thin wrapper around this package.

Refer to godoc here.

Example

The following is an example of how you can use Cascadia.

package main

import (
	"fmt"
	"log"
	"strings"

	"github.com/andybalholm/cascadia"
	"golang.org/x/net/html"
)

var pricingHtml string = `
<div class="card mb-4 box-shadow">
	<div class="card-header">
		<h4 class="my-0 font-weight-normal">Free</h4>
	</div>
	<div class="card-body">
		<h1 class="card-title pricing-card-title">$0/mo</h1>
		<ul class="list-unstyled mt-3 mb-4">
			<li>10 users included</li>
			<li>2 GB of storage</li>
			<li><a href="https://example.com">See more</a></li>
		</ul>
	</div>
</div>

<div class="card mb-4 box-shadow">
	<div class="card-header">
		<h4 class="my-0 font-weight-normal">Pro</h4>
	</div>
	<div class="card-body">
		<h1 class="card-title pricing-card-title">$15/mo</h1>
		<ul class="list-unstyled mt-3 mb-4">
			<li>20 users included</li>
			<li>10 GB of storage</li>
			<li><a href="https://example.com">See more</a></li>
		</ul>
	</div>
</div>

<div class="card mb-4 box-shadow">
	<div class="card-header">
		<h4 class="my-0 font-weight-normal">Enterprise</h4>
	</div>
	<div class="card-body">
		<h1 class="card-title pricing-card-title">$29/mo</h1>
		<ul class="list-unstyled mt-3 mb-4">
			<li>30 users included</li>
			<li>15 GB of storage</li>
			<li><a>See more</a></li>
		</ul>
	</div>
</div>
`

func Query(n *html.Node, query string) *html.Node {
	sel, err := cascadia.Parse(query)
	if err != nil {
		return &html.Node{}
	}
	return cascadia.Query(n, sel)
}

func QueryAll(n *html.Node, query string) []*html.Node {
	sel, err := cascadia.Parse(query)
	if err != nil {
		return []*html.Node{}
	}
	return cascadia.QueryAll(n, sel)
}

func AttrOr(n *html.Node, attrName, or string) string {
	for _, a := range n.Attr {
		if a.Key == attrName {
			return a.Val
		}
	}
	return or
}

func main() {
	doc, err := html.Parse(strings.NewReader(pricingHtml))
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("List of pricing plans:\n\n")
	for i, p := range QueryAll(doc, "div.card.mb-4.box-shadow") {
		planName := Query(p, "h4").FirstChild.Data
		price := Query(p, ".pricing-card-title").FirstChild.Data
		usersIncluded := Query(p, "li:first-child").FirstChild.Data
		storage := Query(p, "li:nth-child(2)").FirstChild.Data
		detailsUrl := AttrOr(Query(p, "li:last-child a"), "href", "(No link available)")
		fmt.Printf(
			"Plan #%d\nName: %s\nPrice: %s\nUsers: %s\nStorage: %s\nDetails: %s\n\n",
			i+1,
			planName,
			price,
			usersIncluded,
			storage,
			detailsUrl,
		)
	}
}

The output is:

List of pricing plans:

Plan #1
Name: Free
Price: $0/mo
Users: 10 users included
Storage: 2 GB of storage
Details: https://example.com

Plan #2
Name: Pro
Price: $15/mo
Users: 20 users included
Storage: 10 GB of storage
Details: https://example.com

Plan #3
Name: Enterprise
Price: $29/mo
Users: 30 users included
Storage: 15 GB of storage
Details: (No link available)