nodejs导出excel----exceljs （1）

导出excel的库

exceljs可导出excel，提供了可支持文件路径及文件流的方式去导出

使用方法

import * as Excel from 'exceljs'; ; // 如果是js则为 var Excel = require('exceljs');
import * as Stream from 'stream';
import { CellData } from '../models/base/zzj-cell.base';
const tinytinycolor  = require('tinytinycolor'); //颜色值的生成

实例化和引入excel

     this.workBook = new Excel.Workbook();
     if(Object.prototype.toString.call(excel) == '[object String]') {
         await this.workBook.xlsx.readFile(<string>excel);
     } else {
         await this.workBook.xlsx.read(excel);
     }

.read(excel)中excel为流，readFile(excel)为excel的文件路径，并且这个两个方法返回都是Promise，可以接着用then继续后续的操作

选取使用worksheet

this.workBook.getWorksheet(this.worksheetNum); //从1开始计数

worksheet中方法

合并了的单元格信息是单独保存了

获取合并单元格的信息

(this.worksheet)._merges; // _开头的方法或变量都是约定的私有的，所以在index.d.ts中没声明，js中就没影响了

mergeCell的结构为

获取单元格的值

官方中提供了遍历每一行每一列的方法

worksheet.eachRow((row, rowNum) => {
    // 遍历每一行
    row.eachCell((cell,col)=>{
        //遍历这一行中的每一个单元格
    });
});

官方提供的这两个方法有个缺点，不管这个单元是否修改了样式和别的属性，只要是没有值都是不会被遍历的，所以

    public eachRow(callBack: EachCellCallback) {
        let row = (this.worksheet)._rows;
        for(let i = 0; i < row.length; i++) {
            if(row[i] == undefined) continue;
            callBack(row[i], i); 
        }        
    }

单元格的数据结构

export interface Cell extends Style, Address {
    readonly worksheet: Worksheet;
    readonly workbook: Workbook;

    readonly effectiveType: ValueType;
    readonly isMerged: boolean;
    readonly master: Cell;
    readonly isHyperlink: boolean;
    readonly hyperlink: string; // todo
    readonly text: string;
    readonly fullAddress: {
        sheetName: string;
        address: Address;
        row: Row;
        col: Column;
    };
    model: CellModel;
    /**
     * Assign (or get) a name for a cell (will overwrite any other names that cell had)
     */
    name: string;

    /**
     * Assign (or get) an array of names for a cell (cells can have more than one name)
     */
    names: string[];

    /**
     * Cells can define what values are valid or not and provide
     * prompting to the user to help guide them.
     */
    dataValidation: DataValidation;

    /**
     * Value of the cell
     */
    value: CellValue;

    /**
     * convenience getter to access the formula
     */
    readonly formula: string;

    /**
     * convenience getter to access the formula result
     */
    readonly result: number | string | Date;

    /**
     * The type of the cell's value
     */
    readonly type: ValueType;

    /**
     * The type of the cell's formula
     */
    readonly formulaType: FormulaType;

    /**
     * The styles of the cell
     */
    style: Partial