绑定onprogress 事件必须使用 addEventListener 方式
xhr.upload.onprogress 上传事件
xhr.onprogress 下载事件
注意：
xhr.upload.addEventListener绑定必须放在xhr.send()之前
加了progress其实是发送了两次请求的
前台js
<body class="m-2">
<label for="a" class="btn btn-primary">点击上传</label>
<input id='a' name="file" type="file" accept="image/png, image/jpeg, video/*" style="display:none;" multiple='multiple'>
<script>
async function main() {
const l = console.log
let fileEle = document.querySelector('#a')
fileEle.onchange = e => {
let files = fileEle.files
if(files.length === 0) return false;
let data = new FormData()
for(const file of files){
data.append('files', file)
}
let xhr = new XMLHttpRequest()
xhr.upload.addEventListener('progress', e => {
if (e.lengthComputable) {
var percentage = Math.round((e.loaded * 100) / e.total);
l(`${percentage}%`)
}
})
xhr.open('post', 'http://localhost:5000/upload')
xhr.responseType = 'json'
xhr.send(data)
xhr.upload.addEventListener('loadstart', e => {
l('上传开始')
})
xhr.upload.addEventListener('error', e => {
l('上传失败')
})
xhr.upload.addEventListener('abort', e => {
l('上传终止')
})
xhr.upload.addEventListener('timeout', e => {
l('由于预设时间到期，上传终止')
})
xhr.upload.addEventListener('load', e => {
l('上传成功了')
})
xhr.upload.addEventListener('loadend', e => {
l('上传已经停止了')
})
xhr.onload = () => {
l(...xhr.response.imgsSrc);
}
}
}
main();
</script>
</body>
</html>
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