element ui 上传文件，读取内容乱码解决

reader.readAsText(file.raw,'gb2312');

<el-upload
                            class="upload-demo"
                            ref="upload"
                            
                            :on-change="handleChange"
                            :file-list="fileList"
                            accept = ".txt"
                            :auto-upload="false">
                            <el-button slot="trigger" size="small" type="primary">选取文件</el-button>
                            
                        </el-upload>

handleChange(file, fileList) {
                var _this = this;
                if (file.raw) {                    
                    let reader = new FileReader()  
                    reader.onload = function (e) {
                       _this.contentHtml = e.target.result;
                    };
                    reader.readAsText(file.raw,'gb2312');
                
                }
                console.log(file, fileList);
            },