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https://github.com/iamacup/react-native-markdown-display

React Native 100% compatible CommonMark renderer
https://github.com/iamacup/react-native-markdown-display

Last synced: 2 months ago
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React Native 100% compatible CommonMark renderer

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README 

        
# React Native Markdown Display [![npm version](https://badge.fury.io/js/react-native-markdown-display.svg)](https://badge.fury.io/js/react-native-markdown-display) [![Known Vulnerabilities](https://snyk.io/test/github/iamacup/react-native-markdown-display/badge.svg)](https://snyk.io/test/github/iamacup/react-native-markdown-display)



It a 100% compatible CommonMark renderer, a react-native markdown renderer done right. This is __not__ a web-view markdown renderer but a renderer that uses native components for all its elements. These components can be overwritten and styled as needed.



### Compatibility with react-native-markdown-renderer



This is intended to be a replacement for react-native-markdown-renderer, with a variety of bug fixes and enhancements - **Due to how the new style rules work, there may be some tweaking needed**, [see how to style stuff section below](#How-to-style-stuff)



### Install



#### Yarn

```npm

yarn add react-native-markdown-display

```



#### NPM

```npm

npm install -S react-native-markdown-display

```



### Get Started



```jsx

import React from 'react';

import { SafeAreaView, ScrollView, StatusBar } from 'react-native';



import Markdown from 'react-native-markdown-display';



const copy = `# h1 Heading 8-)



**This is some bold text!**



This is normal text

`;



const App: () => React$Node = () => {

  return (

    <>

      

      

        

          

            {copy}

          

        

      

    >

  );

};



export default App;

```



### Props and Functions



The `` object takes the following common props:



| Property | Default | Required | Description                                                      

| --- | --- | --- | ---

| `children` | N/A | `true` | The markdown string to render, or the [pre-processed tree](#pre-processing)

| `style` | [source](https://github.com/iamacup/react-native-markdown-display/blob/master/src/lib/styles.js) | `false` | An object to override the styling for the various rules, [see style section below](#rules-and-styles) for more info

| `mergeStyle` | `true` | `false` | If true, when a style is supplied, the individual items are merged with the default styles instead of overwriting them

| `rules` | [source](https://github.com/iamacup/react-native-markdown-display/blob/master/src/lib/renderRules.js) | `false` | An object of rules that specify how to render each markdown item, [see rules section below](#rules) for more info

| `onLinkPress` | `import { Linking } from 'react-native';` and `Linking.openURL(url);` | `false` | A handler function to change click behaviour, [see handling links section below](#handling-links) for more info

| `debugPrintTree` | `false` | `false` | Will print the AST tree to the console to help you see what the markdown is being translated to



And some additional, less used options:



| Property | Default | Required | Description    

| --- | ---  | --- | ---

| `renderer` | `instanceOf(AstRenderer)` | `false` | Used to specify a custom renderer, you can not use the rules or styles props with a custom renderer.

| `markdownit` | `instanceOf(MarkdownIt)` | `false` | A custom markdownit instance with your configuration, default is `MarkdownIt({typographer: true})`

| `maxTopLevelChildren` | `null` | `false` | If defined as a number will only render out first `n` many top level children, then will try to render out `topLevelMaxExceededItem`

| `topLevelMaxExceededItem` | `...` | `false` | Will render when `maxTopLevelChildren` is hit. Make sure to give it a key!

| `allowedImageHandlers` | `['data:image/png;base64', 'data:image/gif;base64', 'data:image/jpeg;base64', 'https://', 'http://']` | `false` | Any image that does not start with one of these will have the `defaultImageHandler` value prepended to it (unless `defaultImageHandler` is null in which case it won't try to render anything)

| `defaultImageHandler` | `http://` | `false` | Will be prepended to an image url if it does not start with something in the `allowedImageHandlers` array, if this is set to null, it won't try to recover but will just not render anything instead.



# Syntax Support



Headings




```

  # h1 Heading 8-)

  ## h2 Heading

  ### h3 Heading

  #### h4 Heading

  ##### h5 Heading

  ###### h6 Heading

```



| iOS | Android

| --- | ---

|   |   






Horizontal Rules




```

  Some text above

  ___



  Some text in the middle



  ---



  Some text below

```



| iOS | Android

| --- | ---

|   |   






Emphasis




```

  **This is bold text**



  __This is bold text__



  *This is italic text*



  _This is italic text_



  ~~Strikethrough~~

```



| iOS | Android

| --- | ---

|   |   






Blockquotes




```

  > Blockquotes can also be nested...

  >> ...by using additional greater-than signs right next to each other...

  > > > ...or with spaces between arrows.

```



| iOS | Android

| --- | ---

|   |   






Lists




```

  Unordered



  + Create a list by starting a line with `+`, `-`, or `*`

  + Sub-lists are made by indenting 2 spaces:

    - Marker character change forces new list start:

      * Ac tristique libero volutpat at

      + Facilisis in pretium nisl aliquet. This is a very long list item that will surely wrap onto the next line.

      - Nulla volutpat aliquam velit

  + Very easy!



  Ordered



  1. Lorem ipsum dolor sit amet

  2. Consectetur adipiscing elit. This is a very long list item that will surely wrap onto the next line.

  3. Integer molestie lorem at massa



  Start numbering with offset:



  57. foo

  58. bar

```



| iOS | Android

| --- | ---

|   |   






Code



  

```

  Inline \`code\`



  Indented code



      // Some comments

      line 1 of code

      line 2 of code

      line 3 of code



  Block code "fences"



  \`\`\`

  Sample text here...

  \`\`\`



  Syntax highlighting



  \`\`\` js

  var foo = function (bar) {

    return bar++;

  };



  console.log(foo(5));

  \`\`\`

```



| iOS | Android

| --- | ---

|   |   






Tables




```

  | Option | Description |

  | ------ | ----------- |

  | data   | path to data files to supply the data that will be passed into templates. |

  | engine | engine to be used for processing templates. Handlebars is the default. |

  | ext    | extension to be used for dest files. |



  Right aligned columns



  | Option | Description |

  | ------:| -----------:|

  | data   | path to data files to supply the data that will be passed into templates. |

  | engine | engine to be used for processing templates. Handlebars is the default. |

  | ext    | extension to be used for dest files. |

```



| iOS | Android

| --- | ---

|   |   






Links




```

  [link text](https://www.google.com)



  [link with title](https://www.google.com "title text!")



  Autoconverted link https://www.google.com (enable linkify to see)

```



| iOS | Android

| --- | ---

|   |   






Images




```

  ![Minion](https://octodex.github.com/images/minion.png)

  ![Stormtroopocat](https://octodex.github.com/images/stormtroopocat.jpg "The Stormtroopocat")



  Like links, Images also have a footnote style syntax



  ![Alt text][id]



  With a reference later in the document defining the URL location:



  [id]: https://octodex.github.com/images/dojocat.jpg  "The Dojocat"

```



| iOS | Android

| --- | ---

|   |   






Typographic Replacements




```

  Enable typographer option to see result.



  (c) (C) (r) (R) (tm) (TM) (p) (P) +-



  test.. test... test..... test?..... test!....



  !!!!!! ???? ,,  -- ---



  "Smartypants, double quotes" and 'single quotes'

```



| iOS | Android

| --- | ---

|   |   






Plugins and Extensions




  Plugins for **extra** syntax support can be added using any markdown-it compatible plugins - [see plugins](https://www.npmjs.com/browse/keyword/markdown-it-plugin) for documentation from markdown-it. An example for integration follows:



#### Step 1



Identify the new components and integrate the plugin with a rendered component. We can use the `debugPrintTree` property to see what rules we are rendering:



```jsx

import React from 'react';

import { SafeAreaView, ScrollView, StatusBar } from 'react-native';



import Markdown, { MarkdownIt } from 'react-native-markdown-display';

import blockEmbedPlugin from 'markdown-it-block-embed';



const markdownItInstance = 

    MarkdownIt({typographer: true})

      .use(blockEmbedPlugin, {

        containerClassName: "video-embed"

      });



const copy = `

# Some header



@[youtube](lJIrF4YjHfQ)

`;



const App: () => React$Node = () => {

  return (

    <>

      

      

        

            

              {copy}

            

        

      

    >

  );

};



export default App;



```



In the console, we will see the following rendered tree:



```

body

-heading1

--textgroup

---text

-video

```



With the following error message:



```

Warning, unknown render rule encountered: video. 'unknown' render rule used (by default, returns null - nothing rendered) 

```



#### Step 2



We need to create the **render rules** and **styles** to handle this new **'video'** component



```jsx

import React from 'react';

import { SafeAreaView, ScrollView, StatusBar } from 'react-native';



import Markdown, { MarkdownIt } from 'react-native-markdown-display';

import blockEmbedPlugin from 'markdown-it-block-embed';



const markdownItInstance = 

    MarkdownIt({typographer: true})

      .use(blockEmbedPlugin, {

        containerClassName: "video-embed"

      });



const copy = `

# Some header



@[youtube](lJIrF4YjHfQ)

`;



const App: () => React$Node = () => {

  return (

    <>

      

      

        

            {

                    // examine the node properties to see what video we need to render

                    console.log(node); // expected output of this is in readme.md below this code snip



                    return (

                      Return a video component instead of this text component!

                    );

                  }

                   

                }}

            >

              {copy}

            

        

      

    >

  );

};



export default App;

```



And all of the video properties needed to render something meaningful are on the node, like this:



```

{type: "video", sourceType: "video", sourceInfo: {…}, sourceMeta: null, block: true, …}

  attributes: {}

  block: true

  children: []

  content: ""

  index: 1

  key: "rnmr_1720a98f540_video"

  markup: "@[youtube](lJIrF4YjHfQ)"

  sourceInfo:

    service: YouTubeService

      env: PluginEnvironment {md: MarkdownIt, options: {…}, services: {…}}

      name: "youtube"

      options:

        height: 390

        width: 640

      serviceName: "youtube"

      videoID: "lJIrF4YjHfQ"

      videoReference: "lJIrF4YjHfQ"

  sourceMeta: null

  sourceType: "video"

  tokenIndex: 5

  type: "video"

```



#### Other Debugging



You can do some additional debugging of what the markdown instance is spitting out like this:



```jsx

import Markdown, { MarkdownIt } from 'react-native-markdown-display';

import blockEmbedPlugin from 'markdown-it-block-embed';



const markdownItInstance = 

    MarkdownIt({typographer: true})

      .use(blockEmbedPlugin, {

        containerClassName: "video-embed"

      });



const copy = `

# Some header



@[youtube](lJIrF4YjHfQ)

`;



// this shows you the tree that is used by the react-native-markdown-display

const astTree = markdownItInstance.parse(copy, {});

console.log(astTree);



//this contains the html that would be generated - not used by react-native-markdown-display but useful for reference

const html = markdownItInstance.render(copy);

console.log(html);



```



The above code will output something like this:



```

astTree:



(4) [Token, Token, Token, Token]



0: Token {type: "heading_open", tag: "h1", attrs: null, map: Array(2), nesting: 1, …}

1: Token {type: "inline", tag: "", attrs: null, map: Array(2), nesting: 0, …}

2: Token {type: "heading_close", tag: "h1", attrs: null, map: null, nesting: -1, …}

3: Token {type: "video", tag: "div", attrs: null, map: Array(2), nesting: 0, …}



length: 4

```



```

html:



Some header




```



All Markdown for Testing




This is all of the markdown in one place for testing that your applied styles work in all cases



```

Headings



  # h1 Heading 8-)

  ## h2 Heading

  ### h3 Heading

  #### h4 Heading

  ##### h5 Heading

  ###### h6 Heading



Horizontal Rules



  Some text above

  ___



  Some text in the middle



  ---



  Some text below



Emphasis



  **This is bold text**



  __This is bold text__



  *This is italic text*



  _This is italic text_



  ~~Strikethrough~~



Blockquotes



  > Blockquotes can also be nested...

  >> ...by using additional greater-than signs right next to each other...

  > > > ...or with spaces between arrows.



Lists



  Unordered



  + Create a list by starting a line with `+`, `-`, or `*`

  + Sub-lists are made by indenting 2 spaces:

    - Marker character change forces new list start:

      * Ac tristique libero volutpat at

      + Facilisis in pretium nisl aliquet. This is a very long list item that will surely wrap onto the next line.

      - Nulla volutpat aliquam velit

  + Very easy!



  Ordered



  1. Lorem ipsum dolor sit amet

  2. Consectetur adipiscing elit. This is a very long list item that will surely wrap onto the next line.

  3. Integer molestie lorem at massa



  Start numbering with offset:



  57. foo

  58. bar



Code



  Inline \`code\`



  Indented code



      // Some comments

      line 1 of code

      line 2 of code

      line 3 of code



  Block code "fences"



  \`\`\`

  Sample text here...

  \`\`\`



  Syntax highlighting



  \`\`\` js

  var foo = function (bar) {

    return bar++;

  };



  console.log(foo(5));

  \`\`\`



Tables



  | Option | Description |

  | ------ | ----------- |

  | data   | path to data files to supply the data that will be passed into templates. |

  | engine | engine to be used for processing templates. Handlebars is the default. |

  | ext    | extension to be used for dest files. |



  Right aligned columns



  | Option | Description |

  | ------:| -----------:|

  | data   | path to data files to supply the data that will be passed into templates. |

  | engine | engine to be used for processing templates. Handlebars is the default. |

  | ext    | extension to be used for dest files. |



Links



  [link text](https://www.google.com)



  [link with title](https://www.google.com "title text!")



  Autoconverted link https://www.google.com (enable linkify to see)



Images



  ![Minion](https://octodex.github.com/images/minion.png)

  ![Stormtroopocat](https://octodex.github.com/images/stormtroopocat.jpg "The Stormtroopocat")



  Like links, Images also have a footnote style syntax



  ![Alt text][id]



  With a reference later in the document defining the URL location:



  [id]: https://octodex.github.com/images/dojocat.jpg  "The Dojocat"



Typographic Replacements



  Enable typographer option to see result.



  (c) (C) (r) (R) (tm) (TM) (p) (P) +-



  test.. test... test..... test?..... test!....



  !!!!!! ???? ,,  -- ---



  "Smartypants, double quotes" and 'single quotes'



```






# Rules and Styles



### How to style stuff



Text styles are applied in a way that makes it much more convenient to manage changes to global styles while also allowing fine tuning of individual elements.



Think of the implementation like applying styles in CSS. changes to the `body` effect everything, but can be overwritten further down the style / component tree.



**Be careful when styling 'text':** the text rule is not applied to all rendered text, most notably list bullet points. If you want to, for instance, color all text, change the `body` style.



Example




 



```jsx

import React from 'react';

import { SafeAreaView, ScrollView, StatusBar } from 'react-native';



import Markdown from 'react-native-markdown-display';



const copy = `

This is some text which is red because of the body style, which is also really small!



\`\`\`

//This is a code block woooo



const cool = () => {

  console.log('????');

};

\`\`\`



and some more small text



# This is a h1

## this is a h2

### this is a h3

`;



const App: () => React$Node = () => {

  return (

    <>

      

      

        

            

              {copy}

            

        

      

    >

  );

};



export default App;

```






### Styles 



Styles are used to override how certain rules are styled. The existing implementation is [here](https://github.com/iamacup/react-native-markdown-display/blob/master/src/lib/styles.js)



**NOTE:** By default styles are merged with the existing implementation, to change this, see the `mergeStyle` prop



Example Implementation




```jsx

import React from 'react';

import { SafeAreaView, ScrollView, StatusBar, StyleSheet } from 'react-native';



import Markdown from 'react-native-markdown-display';



const styles = StyleSheet.create({

  heading1: {

    fontSize: 32,

    backgroundColor: '#000000',

    color: '#FFFFFF',

  },

  heading2: {

    fontSize: 24,

  },

  heading3: {

    fontSize: 18,

  },

  heading4: {

    fontSize: 16,

  },

  heading5: {

    fontSize: 13,

  },

  heading6: {

    fontSize: 11,

  }

});



const copy = `

# h1 Heading 8-)

## h2 Heading 8-)

### h3 Heading 8-)



| Option | Description |

| ------ | ----------- |

| data   | path to data files to supply the data that will be passed into templates. |

| engine | engine to be used for processing templates. Handlebars is the default. |

| ext    | extension to be used for dest files. |

`;



const App: () => React$Node = () => {

  return (

    <>

      

      

        

            

              {copy}

            

        

      

    >

  );

};



export default App;

```






### Rules



Rules are used to specify how you want certain elements to be displayed. The existing implementation is [here](https://github.com/iamacup/react-native-markdown-display/blob/master/src/lib/renderRules.js)



Example Implementation




```jsx

import React from 'react';

import { SafeAreaView, ScrollView, StatusBar, Text } from 'react-native';



import Markdown from 'react-native-markdown-display';



const rules = {

    heading1: (node, children, parent, styles) =>

      

        >> H1 TEXT HERE >> "{children}"

      ,

    heading2: (node, children, parent, styles) =>

      

        >> H2 TEXT HERE >> "{children}"

      ,

    heading3: (node, children, parent, styles) =>

      

        >> H3 TEXT HERE >> "{children}"

      ,

};



const copy = `

# h1 Heading 8-)

## h2 Heading 8-)

### h3 Heading 8-)



| Option | Description |

| ------ | ----------- |

| data   | path to data files to supply the data that will be passed into templates. |

| engine | engine to be used for processing templates. Handlebars is the default. |

| ext    | extension to be used for dest files. |

`;



const App: () => React$Node = () => {

  return (

    <>

      

      

        

            

              {copy}

            

        

      

    >

  );

};



export default App;

```






### All rules and their associated styles:



| Render Rule | Style(s) |

| ------ | ----------- |

| `body` | `body` | 

| `heading1` | `heading1` |

| `heading2` | `heading2` |

| `heading3` | `heading3` |

| `heading4` | `heading4` |

| `heading5` | `heading5` |

| `heading6` | `heading6` | 

| `hr` | `hr` | 

| `strong` | `strong` | 

| `em` | `em` | 

| `s` | `s` | 

| `blockquote` | `blockquote` | 

| `bullet_list` | `bullet_list` | 

| `ordered_list` | `ordered_list` | 

| `list_item` | `list_item` - This is a special case that contains a set of pseudo classes that don't align to the render rule: `ordered_list_icon`, `ordered_list_content`, `bullet_list_icon`, `bullet_list_content` | 

| `code_inline` | `code_inline` | 

| `code_block` | `code_block` | 

| `fence` | `fence` | 

| `table` | `table` | 

| `thead` | `thead` | 

| `tbody` | `tbody` | 

| `th` | `th` | 

| `tr` | `tr` | 

| `td` | `td` | 

| `link` | `link` | 

| `blocklink` | `blocklink` | 

| `image` | `image` | 

| `text` | `text` | 

| `textgroup` | `textgroup` | 

| `paragraph` | `paragraph` | 

| `hardbreak` | `hardbreak` | 

| `softbreak` | `softbreak` | 

| `pre` | `pre` | 

| `inline` | `inline` | 

| `span` | `span` | 



# Handling Links



Links, by default, will be handled with the `import { Linking } from 'react-native';` import and `Linking.openURL(url);` call.



It is possible to overwrite this behaviour in one of two ways:



onLinkPress Callback




```jsx

import React from 'react';

import { SafeAreaView, ScrollView, StatusBar } from 'react-native';



import Markdown from 'react-native-markdown-display';



const copy = `[This is a link!](https://github.com/iamacup/react-native-markdown-display/)`;



const onLinkPress = (url) => {

    if (url) {

      // some custom logic

      return false;

    }

    

    // return true to open with `Linking.openURL

    // return false to handle it yourself

    return true

  }



const App: () => React$Node = () => {

  return (

    <>

      

      

        

          

            {copy}

          

        

      

    >

  );

};



export default App;

```






Using a Custom Rule




You will need to overwrite one or both of `link` and `blocklink`, the original defenitions can be [found here](https://github.com/iamacup/react-native-markdown-display/blob/master/src/lib/renderRules.js)



Something like this with `yourCustomHandlerFunctionOrLogicHere`:



```jsx

import React from 'react';

import { SafeAreaView, ScrollView, StatusBar, Text } from 'react-native';



import Markdown from 'react-native-markdown-display';



const copy = `[This is a link!](https://github.com/iamacup/react-native-markdown-display/)`;



const rules = {

  link: (node, children, parent, styles) => {

    return (

       yourCustomHandlerFunctionOrLogicHere(node.attributes.href) }>

        {children}

      

    );

  },

};



const App: () => React$Node = () => {

  return (

    <>

      

      

        

          

            {copy}

          

        

      

    >

  );

};



export default App;

```






# Disabling Specific Types of Markdown



You can dissable any type of markdown you want, which is very useful in a mobile environment, by passing the markdownit property like below. Note that for convenience we also export the `MarkdownIt` instance so you don't have to include it as a project dependency directly just to remove some types of markdown.



This example will stop images and links.



```jsx

import React from 'react';

import { SafeAreaView, ScrollView, StatusBar, Text } from 'react-native';



import Markdown, { MarkdownIt } from 'react-native-markdown-display';



const copy = `

# This heading will show with formatting



[but this link will just](be displayed as this text)

`;



const App: () => React$Node = () => {

  return (

    <>

      

      

        

            

              {copy}

            

        

      

    >

  );

};



export default App;

```



A full list of things you can turn off is [here](https://github.com/markdown-it/markdown-it/blob/master/lib/presets/commonmark.js)



### Pre Processing



It is possible to need to pre-process the data outside of this library ([related discussion here](https://github.com/iamacup/react-native-markdown-display/issues/79)). As a result, you can pass an AST tree directly as the children like this:



```jsx

import React from 'react';

import { SafeAreaView, ScrollView, StatusBar, Text } from 'react-native';



import Markdown, { MarkdownIt, tokensToAST, stringToTokens } from 'react-native-markdown-display';



const markdownItInstance = MarkdownIt({typographer: true});



const copy = `

# Hello this is a title



This is some text with **BOLD!**

`;



const ast = tokensToAST(stringToTokens(copy, markdownItInstance))



const App: () => React$Node = () => {

  return (

    <>

      

      

        

            

              {ast}

            

        

      

    >

  );

};



export default App;

```



### Other Notes



This is a fork of [react-native-markdown-renderer](https://github.com/mientjan/react-native-markdown-renderer), a library that unfortunately has not been updated for some time so i took all of the outstanding pull requests from that library and tested + merged as necessary.