How to get only text values from a markdown string in Javascript-CodePudding

I currently have some code that uses marked.js to transform one big markdown string (read from a .md file) into html for display on the browser. 'md' is the markdown string and calling 'marked(md)' translates it to html.

getContent(filePath)
        .then(response => {
            if (!response.ok) {
                return Promise.reject(response);
            }
            return response.text().then(md => setContent(marked(md)));
        })
        .catch(e => Dialog.error('Page failed to load!', e));
}, [filePath]);

How can I (either using marked.js, or another solution) parse the markdown/html to get only the text values? Some sample Markdown below.

### HEADER TEXT

---

# Some Page Title

<a href="cafe" target="_blank">Go to Cafe Page</a>

    <Cafe host>/portos/cafe

## Links
- ##### [Tacos](#cafe_tacos)
- ##### [Burritos](#cafe_burritos)
- ##### [Bebidas](#cafe_bebidas)


## Overview
This is the overview text for the page. I really like tacos and burritos.

[![Taco Tabs](some/path/to/images/hello.png 'Tacos')](some/path/to/images/hello.png)

## Dining <a name="dining"></a>

Dining is foo bar burrito taco mulita. 

[![Cafe Overview](some/path/to/images/hello2.png 'Cafe Overview')](some/path/to/images/hello2.png)

The cafe has been open since 1661. It has lots of food.

It was declared the top 1 cafe of all time.

### How to order food

You can order food by ordering food.

<div >
    <strong> Note: </strong> TACOS ARE AMAZING.
</div>

CodePudding user response：

One way to do it is by parsing the HTML string with DOMParser API to turn your string into a Document object and then walk through it with a TreeWalker object to get the textContent of each Text node in the HTML. The result should be an array of strings.

function parseTextFromMarkDown(mdString) {
  const htmlString = marked(mdString);
  const parser = new DOMParser();
  const doc = parser.parseFromString(htmlString, 'text/html');
  const walker = document.createTreeWalker(doc, NodeFilter.SHOW_TEXT);

  const textList = [];
  let currentNode = walker.currentNode;

  while(currentNode) {
    textList.push(currentNode.textContent);
    currentNode = walker.nextNode();
  }

  return textList;
}

CodePudding user response：

While I think Emiel already gave the best answer, another approach would be to use the abstract syntax tree created by Marked's parser, mdast. Then we can walk the syntax tree extracting all the text, combining it into reasonable output. One approach looks like this:

const astToText = ((types) => ({type, children = [], ...rest}) => 
  (types [type] || types .default) (children .map (astToText), rest)
)(Object .fromEntries (Object .entries ({
  'default': () => ` *** Missing type: ${type} *** `,
  'root': (ns) => ns .join ('\n'),
  'heading, paragraph': (ns) => ns .join ('')   '\n',
  'text, code': (ns, {value}) => value,
  'html': (ns, {value}) => 
      new DOMParser () .parseFromString (value, 'text/html') .textContent, 
  'listItem, link, emphasis': (ns) => ns .join (''),
  'list': (ns, {ordered}) => ordered 
      ? ns .map ((n, i) => `${i   1} ${n}`) .join ('\n')
      : ns .map ((n) => `• ${n}`) .join ('\n'),
  'image': (ns, {title, url, alt}) => `Image "${title}" ("${alt}" - ${url})`,
  // ... probably many more
}) .flatMap (([k, v]) => k .split (/,\s*/) .map (n => [n, v]))))

// import {fromMarkdown} from 'mdast-util-from-markdown'
// const ast = fromMarkdown (<your string>)

// dummy version
const ast = {type: "root", children: [{type: "heading", depth:1, children: [{type: "text", value: "Some Page Title", children: []}]}, {type: "paragraph", children: [{type: "html", value: '<a href="cafe" target="_blank">', children: []}, {type: "text", value: "Go to Cafe Page", children: []}, {type: "html", value: "</a>", children: []}]}, {type: "code", lang:null, meta:null, value: "<Cafe host>/portos/cafe", children: []}, {type: "heading", depth:2, children: [{type: "text", value: "Links", children: []}]}, {type: "list", ordered:!1, start:null, spread:!1, children: [{type: "listItem", spread:!1, checked:null, children: [{type: "heading", depth:5, children: [{type: "link", title:null, url: "#cafe_tacos", children: [{type: "text", value: "Tacos", children: []}]}]}]}, {type: "listItem", spread:!1, checked:null, children: [{type: "heading", depth:5, children: [{type: "link", title:null, url: "#cafe_burritos", children: [{type: "text", value: "Burritos", children: []}]}]}]}, {type: "listItem", spread:!1, checked:null, children: [{type: "heading", depth:5, children: [{type: "link", title:null, url: "#cafe_bebidas", children: [{type: "text", value: "Bebidas", children: []}]}]}]}]}, {type: "heading", depth:2, children: [{type: "text", value: "Overview", children: []}]}, {type: "paragraph", children: [{type: "text", value: "This is the overview text for the page. I really like tacos and burritos.", children: []}]}, {type: "paragraph", children: [{type: "link", title:null, url: "some/path/to/images/hello.png", children: [{type: "image", title: "Tacos", url: "some/path/to/images/hello.png", alt: "Taco Tabs", children: []}]}]}, {type: "heading", depth:2, children: [{type: "text", value: "Dining ", children: []}, {type: "html", value: '<a name="dining">', children: []}, {type: "html", value: "</a>", children: []}]}, {type: "paragraph", children: [{type: "text", value: "Dining is foo bar burrito taco mulita.", children: []}]}, {type: "paragraph", children: [{type: "link", title:null, url: "some/path/to/images/hello2.png", children: [{type: "image", title: "Cafe Overview", url: "some/path/to/images/hello2.png", alt: "Cafe Overview", children: []}]}]}, {type: "paragraph", children: [{type: "text", value: "The cafe has been open since 1661. It has lots of food.", children: []}]}, {type: "paragraph", children: [{type: "text", value: "It was declared the top 1 cafe of all time.", children: []}]}, {type: "heading", depth:3, children: [{type: "text", value: "How to order food", children: []}]}, {type: "paragraph", children: [{type: "text", value: "You can order food by ordering food.", children: []}]}, {type: "html", value: '<div >\n    <strong> Note: </strong> TACOS ARE AMAZING.\n</div>', children: []}]}

console .log (astToText (ast))

.as-console-wrapper {max-height: 100% !important; top: 0}

The advantage of this approach over the plain HTML one is that we can decide how certain nodes are rendered in plain text. For instance, here we choose to render this image markup:

![Taco Tabs](some/path/to/images/hello.png 'Tacos')

Image "Tacos" ("Taco Tabs" - some/path/to/images/hello.png)

Of course HTML nodes are still going to be problematic. Here I use DOMParser and .textContent, but you could just add it to text, code to include the raw HTML text.

Each function passed to the configuration receives a list of already formatted children as well as the remainder of the node,