JS筛选器数组根据条件删除重复值

Question

我有一个包含重复元素网的数组

let myArray=[
     {role: "role-1", deviceId: ""},
     {role: "role-2", deviceId: "d-2"},
     {role: "role-3", deviceId: "d-3"},
     {role: "role-1", deviceId: "d-1"},
     {role: "role-2", deviceId: ""},
     {role: "role-4", deviceId: ""}
     {role: "role-5", deviceId: ""}
]

我希望删除重复的角色，并有一个数组，其中包含没有空(“”) deviceIds的角色，如果deviceId是空的，那么用这种方式只保留一个没有重复的角色

myArray=[
         {role: "role-1", deviceId: "d-1"},
         {role: "role-2", deviceId: "d-2"},
         {role: "role-3", deviceId: "d-3"}
         {role: "role-4", deviceId: ""}
         {role: "role-5", deviceId: ""}

 ]

我用这种方式写了这个函数

function dedupeByKey(arr, key) {
  const temp = arr.map(el => el[key]);
  return arr.filter((el, i) =>
    temp.indexOf(el[key]) === i
  );
}

console.log(dedupeByKey(myArray, 'role'));

但是在结果中，它不检查deviceId的值优先，角色与空的deviceId正在增加。怎么解决这个问题？

Answer 1

您可以使用reduce default对象，如果需要，可以在最后将其转换为数组。

​

let myArray = [
     {role: "role-1", deviceId: ""},
     {role: "role-2", deviceId: "d-2"},
     {role: "role-3", deviceId: "d-3"},
     {role: "role-1", deviceId: "d-1"},
     {role: "role-2", deviceId: ""},
     {role: "role-4", deviceId: ""},
     {role: "role-5", deviceId: ""}
]

const res = myArray.reduce((agg, itr) => {
  if (agg[itr.role]) return agg // if deviceId already exist, skip this iteration
  agg[itr.role] = itr.deviceId  // if deviceId not exist, Add it
  return agg
}, {})

let make_array = Object.keys(res).map(key => { return { role: key, deviceId: res[key] }})

console.log(make_array)

​

Answer 2

您可以将唯一角色映射到对象，并将对象还原为数组，如下所示

​

let myArray = [
     {role: "role-1", deviceId: ""},
     {role: "role-2", deviceId: "d-2"},
     {role: "role-3", deviceId: "d-3"},
     {role: "role-1", deviceId: "d-1"},
     {role: "role-2", deviceId: ""},
     {role: "role-4", deviceId: ""},
     {role: "role-5", deviceId: ""}
];

var uniqueObj = myArray.reduce(function(acc, item) {
  var deviceId = acc[item.role] && acc[item.role].deviceId || item.deviceId;
  acc[item.role] = item;
  acc[item.role].deviceId = deviceId;
  return acc;
}, {});

var result = Object.keys(uniqueObj).reduce(function(acc2, item) {
  acc2.push(uniqueObj[item]);
  return acc2;
}, []);

console.log(result);

​

Answer 3

可以对数组中的重复项应用筛选器，以决定筛选索引或保留索引。

​

const myArray= [
     {role: "role-1", deviceId: ""},
     {role: "role-2", deviceId: ""},
     {role: "role-3", deviceId: "d-3"},
     {role: "role-1", deviceId: "d-1"},
     {role: "role-2", deviceId: ""},
     {role: "role-4", deviceId: ""},
     {role: "role-5", deviceId: ""}
]
  
const cleanArray = myArray.filter( (item,index,array) => {
  if ( item.deviceId === "") {
    // filter it out when the same role is found in the array and the index isn't the same as current item you are looking at 
    return !array.some((i,idx) => i.role === item.role && idx > index  )
  }
  return true 
})

// for presentation: sort the array
const sortedArray = cleanArray.sort( (curr, next) => curr.role >  next.role? 1:-1);

console.log(sortedArray)

​