iview的table合并相同的单元格

export default{    data(){        spanb:[]    }},mounted:function(){    let contactDotb = 0;    let spanb = [];    this.data5.forEach((item,index)=>{        if(index === 0){            spanb.push(1)        }else {            if (item.b === this.data5[index - 1].b){                spanb[contactDotb] += 1;                spanb.push(0)            } else {                contactDotb = index                spanb.push(1)            }        }    })   this.spanb = spanb;},methods:{    handleSpan({ row, column, rowIndex, columnIndex }){    if (columnIndex === 1) {        if(this.spanb[rowIndex]){            return {                rowspan:this.spanb[rowIndex],                colspan:1            }        }else{            return {                rowspan: 0,                colspan: 1            }        }    }    if (columnIndex === 2) {        if(this.spanb[rowIndex]){            return {                rowspan:this.spanb[rowIndex],                colspan:1            }        }else{            return {                rowspan: 0,                colspan: 1            }        }    }}}