html 部分

 <input type="file" name="upload" ref="upload" accept=".md" style="display: none" />

js 部分

let input = this.$refs.upload;
input.click();
input.onchange = () => {
    if (input.files && input.files.length > 0 && input.files[0].size > 0) {
        //支持chrome IE10
        if (window.FileReader) {
        let file = input.files[0];
        // let filename = file.name.split(".")[0];
        let reader = new FileReader();
        reader.onloadend = (evt) => {
            // if (evt.target.readyState == FileReader.DONE) {
            console.log(evt.target.result);
            // this.$emit("on-upload-file", evt.target.result);
            // } else {
            //   console.log("error");
            // }
        };
        // 包含中文内容用gbk编码
        reader.readAsText(file, "UTF-8");
        }
        //支持IE 7 8 9 10
        else if (typeof window.ActiveXObject != "undefined") {
        let xmlDoc = new ActiveXObject("Microsoft.XMLDOM");
        xmlDoc.async = false;
        xmlDoc.load(input.value);
        console.log(xmlDoc.xml);
        // this.$emit("on-upload-file", xmlDoc.xml);
        }
        //支持FF
        else if (document.implementation && document.implementation.createDocument) {
        let xmlDoc = document.implementation.createDocument("", "", null);
        xmlDoc.async = false;
        xmlDoc.load(input.value);
        console.log(xmlDoc.xml);
        // this.$emit("on-upload-file", xmlDoc.xml);
        } else {
        // this.$emit("on-upload-file", "该浏览器暂不支持导入文件！");
        console.log("error");
        }
    }
};