性能形容

当 const mergeTable=[2]时，
函数返回
{ rowSpan: 2 }
{ rowSpan: 0 }

当 const mergeTable=[2,3]时,函数返回
{ rowSpan: 2 }
{ rowSpan: 0 }
{ rowSpan: 3 }
{ rowSpan: 0 }
{ rowSpan: 0 }

当const mergeTable=[2,3,3,2]函数返回
{ rowSpan: 2 }
{ rowSpan: 0 }
{ rowSpan: 3 }
{ rowSpan: 0 }
{ rowSpan: 0 }
{ rowSpan: 3 }
{ rowSpan: 0 }
{ rowSpan: 0 }
{ rowSpan: 2 }
{ rowSpan: 0 }

须要优化的函数

性能曾经实现，代码冗余，请问如何优化

// const mergeTable=[2] // 测试 okconst mergeTable = [2, 3]; // 测试ok// const mergeTable=[2,3,3,2]; // 测试ok// 如何简化这个函数function renderRowSpan(index) {  for (let i in mergeTable) {      i=Number(i);    if (i === 0) {      if (index === 0) {        return { rowSpan: mergeTable[0] };      } else if (index < mergeTable[0]) {        return { rowSpan: 0 };      }    }    if (i === 1) {      if (index === mergeTable[0]) {        return { rowSpan: mergeTable[1] };      }      if (index < mergeTable[0] + mergeTable[1]) {        return { rowSpan: 0 };      }    }    if (i === 2) {      if (index === mergeTable[0] + mergeTable[1]) {        return { rowSpan: mergeTable[2] };      }      if (index < mergeTable[0] + mergeTable[1] + mergeTable[2]) {        return { rowSpan: 0 };      }    }      if (i === 3) {          if (index === mergeTable[0] + mergeTable[1]+mergeTable[2]) {              return { rowSpan: mergeTable[3] };          }          if (index < mergeTable[0] + mergeTable[1] + mergeTable[2]+ mergeTable[3]) {              return { rowSpan: 0 };          }      }  }}// 内部办法会渲染indexfor (let index = 0; index < 10; index++) {  console.log(renderRowSpan(index));}