vue 通过xlsx插件实现导出excel

/* eslint-disable */
import { saveAs } from 'file-saver'
import * as XLSX from 'xlsx'
import { Message } from 'element-ui';
import { findTree } from '@/utils'
import store from '@/store'

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_ref = XLSX.utils.encode_cell({
        c: C,
        r: R
      });

      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;
}
/**
 * 实现excel文件下载
 * @param {*} header // 表头 必填
 * @param {*} data // 具体数据 必填
 * @param {*} filename // 非必填
 * @param {*} param3  // 非必填 autoWidth: true, bookType: 'xlsx'
 * @returns 
 */
export function export_json_to_excel(header,data,filename = 'excel-list',{
  multiHeader = [],
  merges = [],
  autoWidth = true,
  bookType = 'xlsx'
} = {}) {
  /* original data */
  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
        };
      }
      /*再判断是否为中文*/
      else if (val.toString().charCodeAt(0) > 255) {
        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'
  });
  try {
    saveAs(new Blob([s2ab(wbout)], {
      type: "application/octet-stream"
    }), `${filename}.${bookType}`);
    Message.success('导出表格成功')
  } catch (e) {
    if (typeof console !== "undefined") console.log(e, wbout);
  }
  return wbout;
}
/**
 * 
 * @param {*} tableData 必填，接口返回的表格数据
 * @param {*} tableColumn 必填，界面显示的列表头数据
 * @param {*} filename 非必填，文件名
 */
export function export_table_to_excel(tableData,tableColumn,filename = 'excel-list') {
  tableData = [...tableData]
  tableColumn = tableColumn.filter(tag => ['index','action'].indexOf(tag.prop) == -1)
  // console.log(tableData, tableColumn)
  // 将表头数据
  const headersArr = tableColumn.map(tag => tag.label)
  // console.log(headersArr)

  // 将表头数据和数据进行对应
  const dataArrs = []
  tableData.forEach(row => {
    const arr = []
    tableColumn.forEach(element => {
      const prop = element.prop
      let val = row[prop]
      if (element.dictionary) {
        const obj =  element.dictionary.find(tag => tag.value === val)
        val = obj ? obj.label : val
      } else if (element.arrName) {
        switch (element.arrName) {
          case 'organizationList':
            val = findTree(store.state.common.organizationList, val, 'name', 'id', 'children')
            break;
          case 'areaData':
            val = findTree(JSON.parse(sessionStorage.getItem('areaData')), val, 'treeNames')
            break;
          case 'userList':
            const user = store.state.common.userList.find(tag => tag.id === val)
            val = user ? user.name : val
            break;
        
          default:
            break;
        }
      }
      arr.push(val)
    })
    dataArrs.push(arr)
  })
  // console.log(dataArrs)
  export_json_to_excel(headersArr, dataArrs, filename)
}