javascript - event.target.result 是空的？

Question

由于某些原因，在下面的代码中，evt.target.result 是空的。这是为什么？

function drop(evt) {
    evt.stopPropagation();
    evt.preventDefault();

    var file = evt.dataTransfer.files[0];

    handleFiles(file, evt.target);
}

function handleFiles(file, target) {
    loadSongAnimate();

    var reader = new FileReader();

    // init the reader event handlers
    reader.onloadend = handleReaderLoadEnd;

    // begin the read operation
    reader.readAsDataURL(file);
}

function handleReaderLoadEnd(evt) {
    alert('Passing this: ' + evt.target.result);
    document.getElementById('audioTagId').src = evt.target.result;
}

Answer 1

来自fine manual :

onloadend
Called when the read is completed, whether successful or not. This is called after either onload or onerror.

我怀疑您遇到了错误情况。添加一个 onerror 回调并查看 reader.error 必须说的内容。您可能希望使用单独的 onerror、onabort 和 onload 回调而不是 onloadend:

onabort
Called when the read operation is aborted.

onerror
Called when an error occurs.

onload
Called when the read operation is successfully completed.

这可能会更容易处理单个事件。

---

在您的评论中，您说您收到来自 other fine manual 的“错误 2” :

Constant: SECURITY_ERR
Value: 2
Description: The file could not be accessed for security reasons.

看来您遇到了“权限被拒绝”错误。