How to overwrite file in FileSystem API

Question

Here is the function:

this.saveObj = function(o, finished)
{   
    root.getDirectory("object", {create: true}, function(directoryEntry)
    {
        directoryEntry.getFile("object.json", {create: true}, function(fileEntry) 
        {
            fileEntry.createWriter(function(fileWriter) 
            {

                fileWriter.onwriteend = function(e) 
                {
                    finished(fileEntry);
                };

                fileWriter.onerror = errorHandler;
                var blob = new Blob([JSON.stringify(o)], {type: "json"});

                fileWriter.write(blob);
            }, errorHandler);
        }, errorHandler);
    }, errorHandler);
};

Now when I save an object everything works fine. Lets say I save {"id":1} my file content would be {"id":1}. Now I edit the object with o = {}; and save it again, my file content suddenly is {} "id":1 }.

It just overwrites the old content, but doesn't clean it. Do I have to delete the file before writing it or is there something I'm missing?

donnywals · Accepted Answer · 2015-02-11 16:01:00Z

1

For as far as I understand the write method will write the supplied content to a position. To me this implies that the existing content is untouched unless you are overwriting parts. So I'm going to say yes, delete the file and save a new one.

source

answered Feb 11, 2015 at 16:01

donnywals

7,6212 gold badges22 silver badges28 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Dirk de Boer · Accepted Answer · 2019-03-16 17:20:30Z

0

According to the Mozilla documentation using only { create: true} :

The existing file or directory is removed and replaced with a new one, then the successCallback is called with a FileSystemFileEntry or a FileSystemDirectoryEntry, as appropriate.

~~Tested in Chrome 72 this seems to be the case.~~

This does not work as the file seems to be persist. The file will be overwritten (first bytes) but the size will remain the same. So this is a bug in at least Chrome 72.

Source

edited Mar 16, 2019 at 17:20

answered Mar 5, 2019 at 20:18

Dirk de Boer

3641 gold badge4 silver badges15 bronze badges

Collectives™ on Stack Overflow

How to overwrite file in FileSystem API

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related