Renaming a File() object in JavaScript

I'd like for my users to be able to re-name a file before uploading it.

I have a File object in Javascript which has a name property that is already set, but i'd like for this to be able to be updated. Right now doing the obvious = "new-name.txt" returns an error that this property is read only.

What's the best way of changing the name property on a JavaScript File object?


You can add an input tag with the name on it and hide the name property from the user. On the server, just use the input as the name and ignore the default name.

Now that is a read-only property, I've found this to be the best method to rename a File object in the browser:

const myNewFile = new File([myFile], 'new_name.png', {type: myFile.type});

try this:

var blob = file.slice(0, file.size, 'image/png'); 
var newFile = new File([blob], 'name.png', {type: 'image/png'});

note: this is for a image type, you have to change this type with type you're actually using.

In response to Alexander Taborda's answer... The first and second parameters of Blob.slice() are the start and end bytes of the original blob that should form the new blob. By saying:

var blob = file.slice(0,-1);

you are not saying "copy to the end of the file" (which is what I think is your aim), you are saying "copy the whole blob except the last byte".

As @carestad says

var blob = file.slice(0, file.size);

followed by creating a new File() object should create an exact copy with a new name.

Note that with a png, the file will be considered invalid without the final byte.


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