借助js的Blob对象FormData对象可以实现大文件分片上传的功能，关于Blob和FormData的具体使用方法可以到如下地址去查看
FormData 对象的使用
Blob 对象的使用
以下是实现代码，本例中后端代码使用php来实现，只是演示基本功能，具体一些文件验证逻辑先忽略。
前段代码：
<!DOCTYPE html><html lang="en"><head> ???<meta charset="UTF-8"> ???<title>upload</title> ???<script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.min.js"></script></head><body> ???<input type="file" name="file" id="file"> ???<button id="upload" onClick="upload()">upload</button> ???<script type="text/javascript"> ???????var bytesPerPiece = 1024 * 1024; // 每个文件切片大小定为1MB . ???????var totalPieces; ???????//发送请求 ???????function upload() { ???????????var blob = document.getElementById("file").files[0]; ???????????var start = 0; ???????????var end; ???????????var index = 0; ???????????var filesize = blob.size; ???????????var filename = blob.name; ???????????//计算文件切片总数 ???????????totalPieces = Math.ceil(filesize / bytesPerPiece); ???????????while(start < filesize) { ???????????????end = start + bytesPerPiece; ???????????????if(end > filesize) { ???????????????????end = filesize; ???????????????} ???????????????var chunk = blob.slice(start,end);//切割文件 ???????????????????var sliceIndex= blob.name + index; ???????????????var formData = new FormData(); ???????????????formData.append("file", chunk, filename); ???????????????$.ajax({ ???????????????????url: ‘http://localhost:9999/test.php‘, ???????????????????type: ‘POST‘, ???????????????????cache: false, ???????????????????data: formData, ???????????????????processData: false, ???????????????????contentType: false, ???????????????}).done(function(res){ ????????????????}).fail(function(res) { ???????????????}); ???????????????start = end; ???????????????index++; ???????????} ???????} ???</script></body></html>后端php代码：
<?phpheader(‘Access-Control-Allow-Origin:*‘);header("Access-Control-Allow-Headers: Origin, X-Requested-With, Content-Type, Accept");$file = $_FILES[‘file‘];$filename = $file[‘name‘];file_put_contents($filename, file_get_contents($file[‘tmp_name‘]), FILE_APPEND);js实现大文件分片上传的方法
原文地址：https://www.cnblogs.com/sghy/p/9143955.html