el-table合并相同日期行方法

spanMethod({ row, column, rowIndex, columnIndex }) {
    if (columnIndex === 0) {
        const prevRow = this.tableData[rowIndex - 1]
        if (prevRow && row.date === prevRow.date) {
            return {
                rowspan: 0,
                colspan: 1
            }
        } else {
            let rowspan = 1
            for (let i = rowIndex + 1; i < this.tableData.length; i++) {
                if (this.tableData[i].date === row.date) {
                    rowspan++
                } else {
                    break
                }
            }
            return {
                rowspan,
                colspan: 1
            }
        }
    }
}