/* eslint-disable */
import { saveAs } from "file-saver";
import * as XLSX from 'xlsx'

function generateArray(table) {
  var out = [];
  var rows = table.querySelectorAll("tr");
  var ranges = [];
  for (var R = 0; R < rows.length; ++R) {
    var outRow = [];
    var row = rows[R];
    var columns = row.querySelectorAll("td");
    for (var C = 0; C < columns.length; ++C) {
      var cell = columns[C];
      var colspan = cell.getAttribute("colspan");
      var rowspan = cell.getAttribute("rowspan");
      var cellValue = cell.innerText;
      if (cellValue !== "" && cellValue == +cellValue) cellValue = +cellValue;

      //Skip ranges
      ranges.forEach(function (range) {
        if (
          R >= range.s.r &&
          R <= range.e.r &&
          outRow.length >= range.s.c &&
          outRow.length <= range.e.c
        ) {
          for (var i = 0; i <= range.e.c - range.s.c; ++i) outRow.push(null);
        }
      });

      //Handle Row Span
      if (rowspan || colspan) {
        rowspan = rowspan || 1;
        colspan = colspan || 1;
        ranges.push({
          s: {
            r: R,
            c: outRow.length,
          },
          e: {
            r: R + rowspan - 1,
            c: outRow.length + colspan - 1,
          },
        });
      }

      //Handle Value
      outRow.push(cellValue !== "" ? cellValue : null);

      //Handle Colspan
      if (colspan) for (var k = 0; k < colspan - 1; ++k) outRow.push(null);
    }
    out.push(outRow);
  }
  return [out, ranges];
}

function datenum(v, date1904) {
  if (date1904) v += 1462;
  var epoch = Date.parse(v);
  return (epoch - new Date(Date.UTC(1899, 11, 30))) / (24 * 60 * 60 * 1000);
}

function sheet_from_array_of_arrays(data, opts) {
  var ws = {};
  var range = {
    s: {
      c: 10000000,
      r: 10000000,
    },
    e: {
      c: 0,
      r: 0,
    },
  };
  for (var R = 0; R != data.length; ++R) {
    for (var C = 0; C != data[R].length; ++C) {
      if (range.s.r > R) range.s.r = R;
      if (range.s.c > C) range.s.c = C;
      if (range.e.r < R) range.e.r = R;
      if (range.e.c < C) range.e.c = C;
      var cell = {
        v: data[R][C],
      };
      if (cell.v == null) continue;
      var cell_address = {c:C, r:R};
      var cell_ref =XLSX.utils.encode_cell(cell_address);

      if (typeof cell.v === "number") cell.t = "n";
      else if (typeof cell.v === "boolean") cell.t = "b";
      else if (cell.v instanceof Date) {
        cell.t = "n";
        cell.z = XLSX.SSF._table[14];
        cell.v = datenum(cell.v);
      } else cell.t = "s";

      ws[cell_ref] = cell;
    }
  }
  if (range.s.c < 10000000) ws["!ref"] = XLSX.utils.encode_range(range);
  return ws;
}

function Workbook() {
  if (!(this instanceof Workbook)) return new Workbook();
  this.SheetNames = [];
  this.Sheets = {};
}

function s2ab(s) {
  var buf = new ArrayBuffer(s.length);
  var view = new Uint8Array(buf);
  for (var i = 0; i != s.length; ++i) view[i] = s.charCodeAt(i) & 0xff;
  return buf;
}

export function export_table_to_excel(id) {
  var theTable = document.getElementById(id);
  var oo = generateArray(theTable);
  var ranges = oo[1];

  /* original data */
  var data = oo[0];
  var ws_name = "SheetJS";

  var wb = new Workbook(),
    ws = sheet_from_array_of_arrays(data);

  /* add ranges to worksheet */
  // ws['!cols'] = ['apple', 'banan'];
  ws["!merges"] = ranges;

  /* add worksheet to workbook */
  wb.SheetNames.push(ws_name);
  wb.Sheets[ws_name] = ws;

  var wbout = XLSX.write(wb, {
    bookType: "xlsx",
    bookSST: false,
    type: "binary",
  });

  saveAs(
    new Blob([s2ab(wbout)], {
      type: "application/octet-stream",
    }),
    "test.xlsx"
  );
}

export function export_json_to_excel({
  multiHeader = [],
  header,
  data,
  filename,
  merges = [],
  autoWidth = true,
  bookType = "xlsx",
} = {}) {
  /* original data */
  filename = filename || "excel-list";
  data = [...data];
  data.unshift(header);

  for (let i = multiHeader.length - 1; i > -1; i--) {
    data.unshift(multiHeader[i]);
  }

  var ws_name = "SheetJS";
  var wb = new Workbook(),
    ws = sheet_from_array_of_arrays(data);

  if (merges.length > 0) {
    if (!ws["!merges"]) ws["!merges"] = [];
    merges.forEach((item) => {
      ws["!merges"].push(XLSX.utils.decode_range(item));
    });
  }

  if (autoWidth) {
    /*设置worksheet每列的最大宽度*/
    const colWidth = data.map((row) =>
      row.map((val) => {
        /*先判断是否为null/undefined*/
        if (val == null) {
          return {
            wch: 10,
          };
        } else if (val.toString().charCodeAt(0) > 255) {
        /*再判断是否为中文*/
          return {
            wch: val.toString().length * 2,
          };
        } else {
          return {
            wch: val.toString().length,
          };
        }
      })
    );
    /*以第一行为初始值*/
    let result = colWidth[0];
    for (let i = 1; i < colWidth.length; i++) {
      for (let j = 0; j < colWidth[i].length; j++) {
        if (result[j]["wch"] < colWidth[i][j]["wch"]) {
          result[j]["wch"] = colWidth[i][j]["wch"];
        }
      }
    }
    ws["!cols"] = result;
  }

  /* add worksheet to workbook */
  wb.SheetNames.push(ws_name);
  wb.Sheets[ws_name] = ws;

  var wbout = XLSX.write(wb, {
    bookType: bookType,
    bookSST: false,
    type: "binary",
  });
  saveAs(
    new Blob([s2ab(wbout)], {
      type: "application/octet-stream",
    }),
    `${filename}.${bookType}`
  );
}

 <template>
  <div id="#app">
    <el-table :data="contentData" border stripe width="500px">
      <el-table-column prop="id" label="id" />
      <el-table-column prop="title" label="title" />
    </el-table>
     <!-- 导出按钮 -->
    <el-button size="default" @click="handleDownload">导出excel</el-button>
  </div>
</template>

<script>
export default {
  data() {
    return {
      contentData: [
        { id: 1, title: "读书" },
        { id: 2, title: "读书" },
        { id: 3, title: "读书" },
        { id: 4, title: "读书" },
      ],
    };
  },
        if (Array.isArray(this.contentData) && this.contentData.length > 0) {
        import("@/vendor/Export2Excel")
          .then((excel) => {
            // excel表示导入的模块对象      //import方法执行完毕返回的是一个promise对象，
            // 在then方法中我们可以拿到使用的模块对象
            // console.log(excel)  //拿到里面的方法
            // const tHeader = ["id", "title"]; // 表头
            // const thName = ["id", "title"]; // 内容
            // 定义每一个对应的中文名称
            const list = {
              id: "序号",
              title: "名称",
            };
            // 提取出一条数据
            const one = this.contentData[0];
            if (!one) {
              return { header, data };
            }
            // 将one数据中的中文名称放入表头数组中
            const tHeader = Object.keys(one).map((key) => {
              return list[key];
            });
            console.log(tHeader);
            // 将one数据中的要使用的key(属性)放入内容数组中
            const thName = Object.keys(one).map((key) => {
              return key;
            });
            // const fileData = this.getOrganData(this.cascaderData, this.organId); // 下载名称
            // 将每一个数据都提取出来组成一个数组(用数据转换的函数将数据转换为一个个的数组)
            const excelData = this.formatJson(thName, this.contentData);// [Array(2), Array(2), Array(2), Array(2)]
            console.log(excelData,'excelData')
            // 调用封装好的函数进行传值(下载)
            excel.export_json_to_excel({
              header: tHeader, // 表头
              data: excelData, // 内容
              // filename: `${fileData.name}(箱)`, // 下载名称
              autoWidth: true, // Optional  // 自适应宽度
              bookType: "xlsx", // Optional // 下载格式
            });
          })
          .catch((error) => {
            console.log(error);
          });
         } else {
          this.$message({
             type: "warning",
             message: "没有有效数据，不能导出",
           });
      },
// 对导出数据格式处理
    formatJson(filterVal, jsonData) {
      return jsonData.map((v) =>
        filterVal.map((j) => {
          if (j === "state") {
            return this.stateFormatter(v);
          }
          if (j === "create_time" || j === "update_time") {
            return parseTime(v[j]);
          } else {
            return v[j];
          }
        })
      );
    },
  },
};
</script>