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I'm experimenting with the HTML5 File API, and I'm needing to use a method which I don't know enough about (simply because it's hardly documented anywhere). I'm talking about the FileWriter truncate() method, and I know it does what I need to do. Basically, rather than appending text to some file data or using seek() to overwrite a certain portion, I want to overwrite all of the data with something else (e.g. from "somedata" to ""). Here's a snippet of the FileWriter setup from HTML5Rocks, with truncate() added in. function onInitFs(fs) { fs.root.getFile('log.txt', {create: false}, function(fileEntry) { // Create a FileWriter object for our FileEntry (log.txt). fileEntry.createWriter(function(fileWriter) { fileWriter.seek(fileWriter.length); // Start write position at EOF. fileWriter.truncate(1); // Create a new Blob and write it to log.txt. var bb = new BlobBuilder(); // Note: window.WebKitBlobBuilder in Chrome 12. bb.append('Hello World'); fileWriter.write(bb.getBlob('text/plain')); }, errorHandler); }, errorHandler); } window.requestFileSystem(window.PERSISTENT, 1024*1024, onInitFs, errorHandler); When it gets to calling writer.truncate(), calling writer.write() throws a File Exception error. I believe this is because the readyState is set to WRITING. Unfortunately, I don't know how to get around that. I've already tried looking through the HTML5Rocks section on this, but it doesn't tell me anything about a truncate() method (although I know it exists from what the Webkit JS Console tells me). Long story short, how I can I use the truncate() method correctly without getting an error?

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