<div id="app">
    <el-upload action="https://jsonplaceholder.typicode.com/posts/" :show-file-list="true" :file-list="fileList" 
      :on-change="imageFileChange" ref="uploadFileRef" multiple>
      <el-button size="mini" style="margin-right:10px">上传文件</el-button>
    </el-upload>
  </div>
  <script>
    let app = new Vue({
      el: "#app",
      data() {
        return {
          fileList: [],
          uploadLoading: null
        }
      },
      methods: {
        imageFileChange(file, fileList) {
          console.log(fileList[0].status);
          console.log(new Date().toLocaleString());
        }
      }
    })
  </script>

触发success状态的原因是开启了自动上传 :auto-upload="true" ,关闭自动上传就不会触发success了。
但我们上传多张图片时，只想一次性上传完，而不是触发一次 on-change事件就上传一次，那要怎么做呢？
方法就是防抖

imageFileChange(file, fileList) {
	if (file.status !== 'ready') return // 阻止上传成功的触发
	console.log(file.status)
	if (this.timer) return
	this.timer = setTimeout(() => {
		this.$confirm('是否覆盖上传？', '提示', {
			confirmButtonText: '确定',
			cancelButtonText: '取消',
			type: 'warning'
		}).then(() => {
			this.uploadLoading = this.$loading({
				lock: true,
				text: '上传中',
				spinner: 'el-icon-loading',
				background: 'rgba(0, 0, 0, 0.7)'
			});
			this.$refs.uploadFileRef.submit()
		}).catch(() => {
		}).finally(() => {
			this.uploadLoading.close()
			this.timer = null
		})
	},100)
}