利用js-xlsx插件实现纯前端导出多级表头excel

1、安装插件

npm install xlsx --save
npm install file-saver --save

2、使用

Export2Excel.js 文件中：

/* eslint-disable */
import { saveAs } from 'file-saver'
import 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_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;
}

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")
}
// 对此方法进行修改，如下：
export function export_json_to_excel({
    multiHeader2 = [],	// 第一行表头
    multiHeader = [], // 第二行表头
    header,	// 第三行表头   在项目中没有使用到三级表头
    data,
    filename, //文件名
    merges = [], // 合并
    autoWidth = true,
    bookType = 'xlsx'
} = {}) {
    /* original data */
    filename = filename || '列表';
    data = [...data]
    // data.unshift(header);

    for (let i = multiHeader2.length - 1; i > -1; i--) {
        data.unshift(multiHeader2[i])
    }

    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
                };
            }
            return {
              'wch': 20
          };
            // /*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'
    });
    saveAs(new Blob([s2ab(wbout)], {
        type: "application/octet-stream"
    }), `${filename}.${bookType}`);
}

vue页面中使用：

    // 导出
    download() {
      // 懒加载，@/utils/Export2Excel 此路径为本地路径
      this.downloadLoading = true
        import('@/utils/Export2Excel').then((excel) => {
          const multiHeader = [
            [
              '单据', '', '', '', '', '', '', '', '', '', '', '', '明细', '', '', '', '', '', '', ''
            ]
          ]
          const header = [
            [
              '日期', '单号', '客户', '大区', '经手人', '代码', '名称', '型号', '编码',
              '单位', '数量', '维修员', '代码', '名称', '型号', '单位', '数量', '性质'
            ]
          ]
          const filterVal = ['billDate', 'billNo', 'customer', 'region', 'makePeople', 'code', 'name', 'model', 'coded', 'unit', 'number', 'people', 'listCode', 'listName', 'listModel', 'listUnit', 'listNumber', 'type']// 表头所对应的字段
          const obj = {}
          for (const key in this.conditions) {
            if (key !== 'page' && key !== 'size' && key !== 'sort') {
              obj[key] = this.conditions[key]
            }
          }
          console.log(obj, '传递值')
          // 去后台获取数据
            creatProcessExcel(obj).then(res => {
              this.downloadLoading = false
              const data = res.map(v => filterVal.map(j => v[j]))
              // 进行所有表头的单元格合并
              const merges = [
                'A1:L1', 'M1:R1', 'A2', 'B2', 'C2', 'D2', 'E2', 'F2', 'G2', 'H2', 'I2', 'J2', 'K2', 'L2', 'M2', 'N2', 'O2', 'P2', 'Q2', 'R2'
              ]
              excel.export_json_to_excel({
                multiHeader, // 这里是第一行的表头
                header, // 这里是第二行的表头
                data,
                filename: '报表',
                merges
              })
            }).catch(err => {
              this.downloadLoading = false
              console.log(err)
            })
            }
        })
    }