How to convert Blob to File in JavaScript

This function converts a Blob into a File and it works great for me.

Vanilla JavaScript

function blobToFile(theBlob, fileName){
    //A Blob() is almost a File() - it's just missing the two properties below which we will add
    theBlob.lastModifiedDate = new Date();
    theBlob.name = fileName;
    return theBlob;
}

TypeScript (with proper typings)

public blobToFile = (theBlob: Blob, fileName:string): File => {
    var b: any = theBlob;
    //A Blob() is almost a File() - it's just missing the two properties below which we will add
    b.lastModifiedDate = new Date();
    b.name = fileName;

    //Cast to a File() type
    return <File>theBlob;
}

Usage

var myBlob = new Blob();

//do stuff here to give the blob some data...

var myFile = blobToFile(myBlob, "my-image.png");

You can use the File constructor:

var file = new File([myBlob], "name");

As per the w3 specification this will append the bytes that the blob contains to the bytes for the new File object, and create the file with the specified name http://www.w3.org/TR/FileAPI/#dfn-file

Joshua P Nixon's answer is correct but I had to set last modified date also. so here is the code.

var file = new File([blob], "file_name", {lastModified: 1534584790000});

1534584790000 is an unix timestamp for "GMT: Saturday, August 18, 2018 9:33:10 AM"