说明
1. 把文件按大小1M分割成N份
2. 每次上传时，告诉后台大文件的md5、当前第几份（从0开始）、总共几份
3. 并行上传，前端同时开启5个请求进行传输增加速度
4. 上传失败或出错后，继续上传下一份，把出错的份放在队尾，如果一直出错则中断请求防止死循环
5. 后台接受文件后通过md5进行比对，上次是否接受过此文件，如果接受则跳过，最后进行文件合并出来
6. 前端代码如下...
7. 查看源代码请点击在线演示地址

<input id="fileInput" type="file" multiple="multiple" name="" /><ul id="box"><!-- <li><span>文件名</span><span>文件类型</span><span>文件大小</span><span>上传进度</span><span>总进度</span><span>操作</span></li><li><span></span><span></span><span></span><span><i><em></em></i><i><em></em></i><i><em></em></i><i><em></em></i><i><em></em></i></span><span><i><em></em></i></span><span><a href="javascript:;">上传</a><a href="javascript:;">暂停</a><a href="javascript:;">删除</a></span></li> -->
</ul>

fileInput.addEventListener('change', function() {var files = this.files;if (files.length) {let str = '<li><span>文件名</span><span>文件类型</span><span>文件大小</span><span>上传进度</span><span>总进度</span><span>操作</span></li>';for (var i = 0; i < files.length; i++) {var file = files[i];str += `<li><span>${file.name}</span><span>${file.type}</span><span>${formatByte(file.size)}</span><span><i><em></em></i><i><em></em></i><i><em></em></i><i><em></em></i><i><em></em></i></span><span><i><b>文件读取中</b></i><i><em></em></i></span><span data-index="${i}"><a data-control="1" href="javascript:;">上传</a><a data-control="2" href="javascript:;">暂停</a><a data-control="3" href="javascript:;">删除</a></span></li>`;}box.innerHTML = str;readFilesStep(0); // 文件太大，同步读取} else {box.innerHTML = ''}
}, false);

function readFilesStep(i) {var files = fileInput.files;if (!files[i]) {return}var oLi = box.children[i + 1];oLi.dataset.count = Math.ceil(files[i].size / SIZE); // 总共多少份var readProgress = oLi.children[4].children[0].children[0];var reader = new FileReader();reader.readAsDataURL(files[i]);reader.onload = function () {oLi.dataset.md5 = md5(this.result);readProgress.innerHTML = '文件读取完毕';readProgress.parentNode.className = 'stop hide';readFilesStep(i + 1);reader = null;}reader.onerror = function (e) {console.error(e);readProgress.innerHTML = '文件读取失败，请重新选择';readFilesStep(i + 1);reader = null;}
}

box.addEventListener('click', function (ev) {var target = ev.target;var control = target.dataset.control;var index = Number(target.parentNode.dataset.index);if (control === "1") {// 上传uploadItem(index);} else if (control === "2") {// 暂停pauseItem(index);} else if (control === "3") {// 删除delItem(index);}
}, false);

var SIZE = 1024 * 1024; // 切片大小
var FETCH_NUM = 5; // 上传文件同时发起请求数
var FETCH_MAP = {}; // 上传请求句柄，取消请求用
var FETCH_POOL = {}; // 每一个上传文件的份数function uploadItem(index) {var file = fileInput.files[index];var oLi = box.children[index + 1];var isPlaying = Number(oLi.dataset.playing) || 0;if (isPlaying) { return }oLi.dataset.playing = 1;var fileMd5 = oLi.dataset.md5;var count = oLi.dataset.count;var lastLoaded = Number(oLi.dataset.lastLoaded || 0);if (!fileMd5) {alert('请等待文件读取')} else {var maxErrorTimes = 10; // 最大出错次数// 第一次点开始会进行创建if (!FETCH_POOL[fileMd5]) {FETCH_POOL[fileMd5] = [];for (var i = 0; i < count; i++) {FETCH_POOL[fileMd5][i] = i;}}FETCH_MAP[fileMd5] = [];for (var i = 0; i < FETCH_NUM; i++) {FETCH_MAP[fileMd5][i] = null;step(i)}function step(i) {var cur = FETCH_POOL[fileMd5].shift();if (cur !== undefined) {FETCH_MAP[fileMd5][i] = uploadStep({file: file, cur: cur, count: count, md5: fileMd5,progressCb: function(e) {var loaded = lastLoaded + e.loaded;setProgress(loaded);var progressItem = (e.loaded / e.total * 100).toFixed(2) + '%';var oProgressItem = oLi.children[3].children[i];oProgressItem.title = progressItem;oProgressItem.children[0].style.width = progressItem;if (progressItem === '100.00%') {oProgressItem.className = 'stop'} else {oProgressItem.className = ''}}, successCb: function(){lastLoaded += SIZE;setProgress(lastLoaded, true);step(i);}, errorCb: function(status) {// 失败把当前份放在末尾，继续下一步FETCH_POOL[fileMd5].push(cur);if (status === 0) {// 手动取消 暂停} else if (maxErrorTimes--) {// 出错10次后不再上传，防止进入死循环step(i);}}});}}function setProgress(loaded, isFinished) {var oProgress = oLi.children[4].children[1];// 实际上传的数据大小 > 文件大小，此处做修正处理if (loaded > file.size) {if (isFinished) {loaded = file.size;oProgress.className = 'stop';} else {loaded = file.size * 0.9999;}}oLi.children[2].innerHTML = formatByte(loaded) + '/' + formatByte(file.size);var progress = (loaded / file.size * 100).toFixed(2) + '%';var lastProgress = oProgress.title || '0%';// 并行上传 此处可能是线路1的进度和线路2的进度比较,优先显示最大值progress = parseFloat(lastProgress) < parseFloat(progress) ? progress : lastProgress;// 总进度条oProgress.title = progress;oProgress.children[0].style.width = progress;if (isFinished) {oLi.dataset.lastLoaded = loaded;}}}
}

function uploadStep(obj) {var file = obj.file;var cur = obj.cur;var fileMd5 = obj.md5;var count = obj.count;var progressCb = obj.progressCb;var successCb = obj.successCb;var errorCb = obj.errorCb;var params = new FormData();var filename = file.name;var fileChunk = file.slice(SIZE * cur, SIZE * (cur + 1));params.append('md5', fileMd5);params.append('file', fileChunk);params.append('cur', cur);params.append('count', count);var xhr = new XMLHttpRequest();xhr.onreadystatechange = function () {if (xhr.readyState == 4) {if (xhr.status == 200) {successCb && successCb(JSON.parse(xhr.responseText))} else {errorCb && errorCb(xhr.status)}}}xhr.upload.onprogress = function (e) {progressCb && progressCb(e)}xhr.open('POST', '/api/upload', true);xhr.send(params);return xhr;
}function formatByte(b) {var kb = b / 1024;if (kb >= 1024) {var m = kb / 1024;if (m >= 1024) {var g = m / 1024;return g.toFixed(2) + 'G';} else {return m.toFixed(2) + 'M';}} else {return kb.toFixed(2) + 'K';}
}

function pauseItem(index) {var file = fileInput.files[index];var oLi = box.children[index + 1];var isPlaying = Number(oLi.dataset.playing) || 0;if (!isPlaying) { return }oLi.dataset.playing = 0;var fileMd5 = oLi.dataset.md5;for (var i = 0; i < FETCH_MAP[fileMd5].length; i++) {if (FETCH_MAP[fileMd5][i]) {FETCH_MAP[fileMd5][i].abort();FETCH_MAP[fileMd5][i] = null;}}
}

function delItem(index) {var file = fileInput.files[index];var oLi = box.children[index + 1];var fileMd5 = oLi.dataset.md5;oLi.className = 'hide';if (FETCH_MAP[fileMd5]) {for (var i = 0; i < FETCH_MAP[fileMd5].length; i++) {if (FETCH_MAP[fileMd5][i]) {FETCH_MAP[fileMd5][i].abort();FETCH_MAP[fileMd5][i] = null;}}}
}