golang 将html转换为markdown

html-to-markdown 可以将html转换为markdown。

Convert HTML into Markdown with Go. It is using an HTML Parser to avoid the use of regexp as much as possible. That should prevent some weird cases and allows it to be used for cases where the input is totally unknown.

Installation

go get github.com/JohannesKaufmann/html-to-markdown

Usage

import (
	"fmt"
	"log"

	md "github.com/JohannesKaufmann/html-to-markdown"
)

converter := md.NewConverter("", true, nil)

html := `<strong>Important</strong>`

markdown, err := converter.ConvertString(html)
if err != nil {
  log.Fatal(err)
}
fmt.Println("md ->", markdown)

If you are already using goquery you can pass a selection to Convert.

markdown, err := converter.Convert(selec)

Using it on the command line

If you want to make use of html-to-markdown on the command line without any Go coding, check out html2md, a cli wrapper for html-to-markdown that has all the following options and plugins builtin.

Options

The third parameter to md.NewConverter is *md.Options.

For example you can change the character that is around a bold text (”**”) to a different one (for example “__”) by changing the value of StrongDelimiter.

opt := &md.Options{
  StrongDelimiter: "__", // default: **
  // ...
}
converter := md.NewConverter("", true, opt)

For all the possible options look at godocs and for a example look at the example.

Adding Rules

converter.AddRules(
  md.Rule{
    Filter: []string{"del", "s", "strike"},
    Replacement: func(content string, selec *goquery.Selection, opt *md.Options) *string {
      // You need to return a pointer to a string (md.String is just a helper function).
      // If you return nil the next function for that html element
      // will be picked. For example you could only convert an element
      // if it has a certain class name and fallback if not.
      content = strings.TrimSpace(content)
      return md.String("~" + content + "~")
    },
  },
  // more rules
)

For more information have a look at the example add_rules.

Using Plugins

If you want plugins (github flavored markdown like striketrough, tables, …) you can pass it to Use.

import "github.com/JohannesKaufmann/html-to-markdown/plugin"

// Use the `GitHubFlavored` plugin from the `plugin` package.
converter.Use(plugin.GitHubFlavored())

Or if you only want to use the Strikethrough plugin. You can change the character that distinguishes the text that is crossed out by setting the first argument to a different value (for example “~~” instead of “~”).

converter.Use(plugin.Strikethrough(""))

For more information have a look at the example github_flavored.

Writing Plugins

Have a look at the plugin folder for a reference implementation. The most basic one is Strikethrough.

Security

This library produces markdown that is readable and can be changed by humans.

Once you convert this markdown back to HTML (e.g. using goldmark or blackfriday) you need to be careful of malicious content.

This library does NOT sanitize untrusted content. Use an HTML sanitizer such as bluemonday before displaying the HTML in the browser.

Other Methods

Godoc

func (c *Converter) Keep(tags ...string) *Converter

Determines which elements are to be kept and rendered as HTML.

func (c *Converter) Remove(tags ...string) *Converter

Determines which elements are to be removed altogether i.e. converted to an empty string.