Deprecated: This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.
Non-standard: This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
The FileSystemEntry interface's method toURL() creates and returns a string containing a URL which can be used to identify the file system entry. This is done by exposing a new URL scheme—filesystem:—that can be used as the value of src and href attributes.
A string containing a URL that can then be used as a document reference in HTML content, or an empty string if the URL can't be generated (such as if the file system implementation doesn't support toURL()).
If you have a FileSystemFileEntry corresponding to an image file in a file system available to your website or app, you can call toURL() to get its URL for use in HTML. If your site is located at http://my-awesome-website.woot, and you have a temporary file system that contains an image file named awesomesauce.jpg, the URL returned by toURL() might be (depending on the browser's implementation) something like "filesystem:http://my-awesome-website.woot/temporary/awesomesauce.jpg".
Code that makes use of this might look like this:
let img = document.createElement("img");
img.src = imageFileEntry.toURL();
document.body.appendChild(img);
Assuming the scenario mentioned before the code, the result would be HTML that looks like this being appended to the end of the document:
<img
src="filesystem:http://my-awesome-website.woot/temporary/awesomesauce.jpg" />