Reading files in a Chrome Extension
03 Mar 2018Often, it is desirable for a Chrome extension to be bundled with files that need to be read. These files may contain data or configuration information to help the extension function. This short guide will show you how you can set up your Chrome extension to read files.
Add file path(s) to manifest.json
Firstly, you must add the file paths to the web_accessible_resources property
in the manifest.json file. The file paths are relative to the extension’s root (where
the manifest.json is located). For instance, if I wanted to include a file
called info.json that is located in a folder data, it would look like:
"web_accessible_resources": [
"data/info.json"
]
A cool feature is that these paths support wildcards. For example:
"web_accessible_resources": [
"data/*.json"
]
will allow access to any json file in the data folder.
Read from the file
The next step is to read the data from the file. To do this, we need to get the URL of the file and make a request to it.
To get the URL of the file we can use chrome.runtime.getURL('path/to/file').
Then we make a GET request to the URL. In this example, we will use the ES6 feature Fetch but methods such as XmlHttpRequest will also work.
const url = chrome.runtime.getURL('path/to/file');
fetch(url)
.then((response) => {response.json()}) //assuming file contains json
.then((json) => doSomething(json));
And there we have it!
To reiterate the steps simply:
- Add file path to the
web_accessible_resourcesproperty in themanifest.jsonfile - Get the URL of the file using
chrome.runtime.getURL('path/to/file') - Make a GET request to the URL