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react-native-html-webview

Display (possibly untrusted) HTML using a UIWebView in React Native.

Uses an HTML Sanitizer to remove only let through a whitelist of tags and attributes (so it removes all javascript). Also supports automatically adjusting the height of the webview to contain the contents you give it.

Written by Thomas Parslow (almostobsolete.net and tomparslow.co.uk) as part of Active Inbox (activeinboxhq.com).

A couple of similar projects are HTMLText and HTMLView both of which render a subset of HTML as React Native views. This project takes a slightly different approach of using a UIWebView giving a full HTML renderer, but that means it has to rely on an HTML sanitizer to clean up untrusted HTML.

Installation

Install using npm with npm install --save react-native-html-webview

You then need to add the Objective C part to your XCode project. Drag AIBHTMLWebView.xcodeproj from the node_modules/react-native-html-webview folder into your XCode projec. Click on the your project in XCode, goto Build Phases then Link Binary With Libraries and add libAIBHTMLWebView.a.

NOTE: Make sure you don't have the AIBHTMLWebView project open seperately in XCode otherwise it won't work.

Usage

var HTMLWebView = require('react-native-html-webview');

var testView = React.createClass({
  render: function() {
    return (
      <View>
        <HTMLWebView
            style={{width: 300}}
            html={this.state.htmlContents}
            makeSafe={true}
            autoHeight={true}
            onLink={this.onLink}/>
      </View>
    );
  },
  onLink: function (href) {
    // Link was clicked!
  }
});

Properties

  • html : The html content to display as a string
  • makeSafe (default: true) : Run the HTML through an HTML sanitizer (safe-html) before inserting it to remove script tags and similar unsafe things. Pass in true to use the default options for safe-html, pass in false to turn it off, or pass in an object to set config options for safe-html.
  • autoHeight (default: false) : Automatically adjust the height of the webview to fit the contents (also turns off scrolling).
  • onLink : Pass in a function to be called when the user clicks a link, the function will be given the href.

Security Warning

This relies on HTML sanitization to protect you from executing JavaScript included in untrusted HTML. It's using my safe-html library which works based on a whitelist of allowed tags but it's still possbile someone could find a way round it.

If an attacker did find a way round the sanitizer they'd still only be running JavaScript inside a WebView. So they wouldn't automatically get access to the rest of your app, but they would be able to load other stuff into the webview and possibly other stuff that you may not want.

Feedback Welcome!

Feedback, questions, suggestions and most of all Pull Requests are very welcome. This is an early version and I want to figure out the best way to continue it.

I'm also available for freelance work!

I'm @almostobsolete on Twitter my email is tom@almostobsolete.net and you can find me on the web at tomparslow.co.uk and almostobsolete.net