javascript - 上传前如何操作内存中的文件流

Question

我正在开发一个上传程序，需要在上传数据之前将其覆盖为预定值来审查上传数据中的一些字节。

现在，我已连接到 onSubmit 事件，因为它允许执行非阻塞工作。您可以在下面看到我的事件处理程序。在调用 promise.success(); 之前，您会注意到大量注释的部分，这就是我需要帮助的问题。如何在那里返回/设置字节数组？

onSubmit: function (id, name) {
    // http://docs.fineuploader.com/branch/master/api/events.html#submit
    // Called when the item has been selected and is a candidate for uploading.
    // Return false to prevent submission to the uploader.

    // create promise
    var promise = new qq.Promise();

    // configure file reader
    var reader = new FileReader();
    reader.onerror = function (e) {
        promise.failure("error occured reading file");
    };
    reader.onabort = function (e) {
        promise.failure("file reading aborted");
    };
    reader.onload = function (e) {
        var buffer = reader.result;
        var byteArray = new Uint8Array(buffer);

        manipulateByteArray(byteArray);

        /******************* Missing part... **********************/
        // TODO (How to return manipulated byteArray?)
        /******************* Missing part...**********************/

        // signal success
        promise.success();
    }

    // initiate async work
    var file = this.getFile(id);
    reader.readAsArrayBuffer(file);

    // return promise
    return promise;
},

Answer 1

我明白了。这是关键部分:

        if(needsManipulation(byteArray))
        {
            manipulateByteArray(byteArray);

            // construct a new blob
            var newBlob = { blob: new Blob([byteArray], { type: 'application/octet-stream' }), name: name };

            // restart the process for the adjusted file
            uploader.addFiles(newBlob);

            // signal failure and exit early
            promise.failure();
            return;
        }

这是修改后的代码:

onSubmit: function (id, name) {
    // http://docs.fineuploader.com/branch/master/api/events.html#submit
    // Called when the item has been selected and is a candidate for uploading.
    // Return false to prevent submission to the uploader.

    // create promise
    var promise = new qq.Promise();

    // add uploader instance to closure
    var uploader = this;

    // configure file reader
    var reader = new FileReader();
    reader.onerror = function (e) {
        promise.failure("error occured reading file");
    };
    reader.onabort = function (e) {
        promise.failure("file reading aborted");
    };
    reader.onload = function (e) {
        var buffer = reader.result;
        var byteArray = new Uint8Array(buffer);

        if(needsManipulation(byteArray))
        {
            manipulateByteArray(byteArray);

            // construct a new blob
            var newBlob = { blob: new Blob([byteArray], { type: 'application/octet-stream' }), name: name };

            // restart the process for the adjusted file
            uploader.addFiles(newBlob);

            // signal failure and exit early
            promise.failure();
            return;
        }

        // signal success
        promise.success();
    }

    // initiate async reading work
    var file = this.getFile(id);
    reader.readAsArrayBuffer(file);

    // return promise
    return promise;
},