调用 ajax-process接口显示上传进度

使用ajax上传文件的时候为了通过 files api来获取文件信息,从而可以看到显示进度
html

   <div class="row">
            <label for="file">
                Upload Image:</label>
            <input type="file" name="fileToUpload" id="fileToUpload"  multiple="multiple" onchange="fileSelected();" />
        </div>

        <div id="fileName">
        </div>
        <div id="fileSize">
        </div>
        <div id="fileType">
        </div>
        <div class="row">
            <input type="button" onclick="uploadFile()" value="Upload Image" />
        </div>
        <div id="progressNumber">
        </div>

js

        function fileSelected() {
            var file = document.getElementById('fileToUpload').files[0];
            if (file) {
                var fileSize = 0;
                if (file.size > 1024 * 1024)
                    fileSize = (Math.round(file.size * 100 / (1024 * 1024)) / 100).toString() + 'MB';
                else
                    fileSize = (Math.round(file.size * 100 / 1024) / 100).toString() + 'KB';

                document.getElementById('fileName').innerHTML = 'Name: ' + file.name;
                document.getElementById('fileSize').innerHTML = 'Size: ' + fileSize;
                document.getElementById('fileType').innerHTML = 'Type: ' + file.type;
            }
        }

        function uploadFile() {
            var fd = new FormData();
            fd.append("fileToUpload", document.getElementById('fileToUpload').files[0]);
            var xhr = new XMLHttpRequest();
            xhr.upload.addEventListener("progress", uploadProgress, false);
            xhr.addEventListener("load", uploadComplete, false);
            xhr.addEventListener("error", uploadFailed, false);
            xhr.addEventListener("abort", uploadCanceled, false);
            xhr.open("POST", "Home/Upload");
            xhr.send(fd);
        }

        function uploadProgress(evt) {
            if (evt.lengthComputable) {
                var percentComplete = Math.round(evt.loaded * 100 / evt.total);
                document.getElementById('progressNumber').innerHTML = percentComplete.toString() + '%';
            }
            else {
                document.getElementById('progressNumber').innerHTML = 'unable to compute';
            }
        }

        function uploadComplete(evt) {
            /* This event is raised when the server send back a response */
            alert(evt.target.responseText);
        }

        function uploadFailed(evt) {
            alert("There was an error attempting to upload the file.");
        }

        function uploadCanceled(evt) {
            alert("The upload has been canceled by the user or the browser dropped the connection.");
        }

这里加了一个监听事件,可以通过异步来不断获取上传信息,从而能正常的显示上传进度

文章来源
另一个资料-使用 JavaScript File API 实现文件上传

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