使用fileAPI 可以实现本地文件读取，可以实现将本地文件内容直接post，而不是文件本身

参考文档https://www.html5rocks.com/zh/tutorials/file/dndfiles/

 <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<input type="file" id="files" name="files"/>
<output id="list"></output>
<script>
    function handleFileSelect(evt) {
        var files = evt.target.files; // FileList object
        for (var i = 0, f; f = files[i]; i++) {
            var reader = new FileReader();
            reader.onload = (function (theFile) {
                return function (e) {
                    var span = document.createElement('span');
                    span.innerHTML = e.target.result;
                    document.getElementById('list').insertBefore(span, null);
                };
            })(f);
            reader.readAsText(f);
        }
    }

    document.getElementById('files').addEventListener('change', handleFileSelect, false);
</script>

</body>
</html>