为什么我无法获取到datas的长度?
materialdata里的数据为 : [{"material_id":"of6","material_name":"西米","status":0},{"material_id":"rVr","material_name":"寒天晶球","status":0}]
```javascript
var res=[]
try {
res = await mysql.query("select materialdata from group_tea_relations where tea_id=?",[teaIds[i].tea_id])
} catch(e) {
console.error(e)
}
var datas=[]
datas=JSON.parse(res[0].materialdata)
console.log(datas.length)
for(let g=0;g<datas.length;g++){
datas[g].status=0
}
```
