如何在JavaScript中将Blob转换为File

Question

我需要将图像上传到NodeJS服务器到某个目录.我正在使用connect-busboy节点模块.

我dataURL使用以下代码将我转换为blob的图像:

dataURLToBlob: function(dataURL) {
    var BASE64_MARKER = ';base64,';
    if (dataURL.indexOf(BASE64_MARKER) == -1) {
        var parts = dataURL.split(',');
        var contentType = parts[0].split(':')[1];
        var raw = decodeURIComponent(parts[1]);
        return new Blob([raw], {type: contentType});
    }
    var parts = dataURL.split(BASE64_MARKER);
    var contentType = parts[0].split(':')[1];
    var raw = window.atob(parts[1]);
    var rawLength = raw.length;
    var uInt8Array = new Uint8Array(rawLength);
    for (var i = 0; i < rawLength; ++i) {
        uInt8Array[i] = raw.charCodeAt(i);
    }
    return new Blob([uInt8Array], {type: contentType});
}

我需要一种方法将blob转换为文件以上传图像.

有人可以帮我吗？

Answer 1

您可以使用File构造函数:

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

根据w3规范,这将将blob包含的字节附加到新File对象的字节,并创建具有指定名称的文件 http://www.w3.org/TR/FileAPI/#dfn-file

Answer 2

此函数将a转换Blob为a File,它对我来说非常有用.

香草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(正确的打字)

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;
}

用法

var myBlob = new Blob();

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

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

Answer 3

为了让我工作，我必须明确提供类型，尽管它包含在 blob 中：

const file = new File([blob], 'untitled', { type: blob.type })

Answer 4

打字稿

public blobToFile = (theBlob: Blob, fileName:string): File => {       
    return new File([theBlob], fileName, { lastModified: new Date().getTime(), type: theBlob.type })
}

Javascript

function blobToFile(theBlob, fileName){       
    return new File([theBlob], fileName, { lastModified: new Date().getTime(), type: theBlob.type })
}

输出

File {name: "fileName", lastModified: 1597081051454, lastModifiedDate: Mon Aug 10 2020 19:37:31 GMT+0200 (Eastern European Standard Time), webkitRelativePath: "", size: 601887, …}
lastModified: 1597081051454
lastModifiedDate: Mon Aug 10 2020 19:37:31 GMT+0200 (Eastern European Standard Time) {}
name: "fileName"
size: 601887
type: "image/png"
webkitRelativePath: ""
__proto__: File

Answer 5

约书亚·尼克松（Joshua P Nixon）的回答是正确的，但我也必须设定最后修改日期。所以这是代码。

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

1534584790000是Unix时间戳“ GMT：星期六，2018年8月18日上午九时33分10秒 ”

Answer 6

我的现代变体:

function blob2file(blobData) {
  const fd = new FormData();
  fd.set('a', blobData);
  return fd.get('a');
}

Answer 7

var blob = new Blob(["Hello, world!"], { type: "text/plain;charset=utf-8" });

var file = new File([blob], "name.txt");

现在您可以上传为 .txt 文件