let a=[ {key:0,name:'tom',child:[{id:"fdfsds",age:18}]}, {key:0,name:'tom1',child:[{id:"greher",age:18}]}, {key:0,name:'tom2',child:[{id:"tryyty",age:18}]}, {key:0,name:'tom3',child:[{id:"khjky",age:18}]},
]
let b=[]
a.forEach((value,index)=>{
b[index]=value
b[index].child=value.child.filter(item=>item.id!="fdfsds")
})
