HTML5 file api读取文件的MD5码工具

1、工具的用途：用HTML5 file api读取文件的MD5码。MD5码在文件的唯一性识别上有很重要的应用，业内常用MD5进行文件识别、文件秒传、文件安全性检查等；

2、适用性：IE、Chrome皆兼容；

3、缺陷：当上传大文件时，需要较长的时间才能扫描出MD5码；

4、关于引用：其中引用了js文件（spark-md5.js）

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8">

    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">

    <title>HTML5 read files hash</title>
    <meta name="author" content="Mofei">
    <meta name="viewport" content="width=device-width; initial-scale=1.0;">
    <script src="spark-md5.js" type="text/javascript"></script>
</head>

<body>
    <div>
        <header>
            <h1>HTML5 read files hash</h1>
        </header>
        <div>
            <input type="file" id="file">
            <div id="box"></div>
        </div>
        <footer>
            <p>&copy; Copyright  by Percy(<a href="http://www.cnblogs.com/Percy_Lee/">www.cnblogs.com/Percy_Lee</a>)</p>
        </footer>
    </div>

    <script type="text/javascript">
     document.getElementById("file").addEventListener("change", function () {
        var fileReader = new FileReader(),
            box = document.getElementById('box'),
            blobSlice = File.prototype.mozSlice || File.prototype.webkitSlice || File.prototype.slice,
            file = document.getElementById("file").files[0],
            chunkSize = 2097152,
            chunks = Math.ceil(file.size / chunkSize),
            currentChunk = 0,
            bs = fileReader.readAsBinaryString,
            spark = bs ? new SparkMD5() : new SparkMD5.ArrayBuffer();

        fileReader.onload = function (ee) {
            spark.append(ee.target.result);
            currentChunk++;

            if (currentChunk < chunks) {
                loadNext();
            } else {
                box.innerText = 'MD5:  ' + spark.end();
            }
        }

        function loadNext() {
            var start = currentChunk * chunkSize, end = start + chunkSize >= file.size ? file.size : start + chunkSize;
            if (bs) fileReader.readAsBinaryString(blobSlice.call(file, start, end));
            else fileReader.readAsArrayBuffer(blobSlice.call(file, start, end));
        }

        loadNext();
    });

    </script>
</body>
</html>