var result = updateObj(objList, newObj);
console.log(result);

function updateObj(list, newobj){
  var flatarr = list.map(e=>Object.entries(e).map(([k, val]) => val)).flat(3);
  var filterService =  newobj.filter(e=>e.name=="service");
  //got stuck
}

var newObj=[{
    "id": "service",
    "name": "bank",
    "amount": 2000
},{
    "id": "service",
    "name": "credit",
    "amount": 5000
}]


var objList=[
{
  "btob": [{
    "id": "service",
    "name": "bank",
    "amount": 1000
  },{
    "id": "fund",
    "name": "bank",
    "amount": 2000
  },{
    "id": "others",
    "name": "bank",
    "amount": 5000
   }]
},{
 "ctob":[{
    "id": "service",
    "name": "credit",
    "amount": 1000,
    "rate": 0.4
  },{
    "id": "fund",
    "name": "credit",
    "amount": 3000,
    "rate": 0.2
  },{
    "id": "others",
    "name": "credit",
    "amount": 4000,
    "rate": 0.6
   }]
  }]
}]

var result=[
{
  "btob": [{
    "id": "service",
    "name": "bank",
    "amount": 2000
  },{
    "id": "fund",
    "name": "bank",
    "amount": 2000
  },{
    "id": "others",
    "name": "bank",
    "amount": 5000
   }]
},{
 "ctob":[{
    "id": "service",
    "name": "credit",
    "amount": 5000,
    "rate": 0.4
  },{
    "id": "fund",
    "name": "credit",
    "amount": 3000,
    "rate": 0.2
  },{
    "id": "others",
    "name": "credit",
    "amount": 4000,
    "rate": 0.6
   }]
  }]
}]