检查 ID 是否在 ES6 中找到另一个数组

Question

I wanted to filter out the data. I wanted to check if data on data1 is found on data2 and to check if it has errorMessages. Please check my code below. Is there a better way to do it?

data1

[
    {
        "ids": "0111",  
    },
    {
        "ids": "0222",
    },
    {
         "ids": "0333",
    }
]

data2

[
  {
    "id": "0111",
    "errorMessages": [
      {
        "message": ["sample error message 1"]
      }
    ]
  },
  {
    "id": "0333",
    "errorMessages": []
  }
]

Code

const output= data1.filter(
  (element) => element.ids === data2.find((data) => data).id
);

console.log("output", output);

Answer 1

.find((data) => data) doesn't do anything useful - each item in the array is an object, which is truthy, so that'll always return the first element in the array.

If you did want to .find a matching element in the other array - then a better approach would be to make a Set of the IDs found in the other array first (Set lookup is much quicker - O(1) - than .find , which is O(n) ).

You also need to implement the logic to check if the errorMessages is empty.

 const data1 = [ { "ids": "0111", }, { "ids": "0222", }, { "ids": "0333", } ] const data2 = [ { "id": "0111", "errorMessages": [ { "message": ["sample error message 1"] } ] }, { "id": "0333", "errorMessages": [] } ] const ids = new Set( data2.filter(item => item?.errorMessages.length).map(item => item.id) ); const output= data1.filter( element => ids.has(element.ids) ); console.log("output", output);

Answer 2

Without Set, but use Object as the map.

const IDKeys = {};

data2.forEach(data => {
    if (data.errorMessages.length){
       IDKeys[data.id] = true; // means valid 
    }
})


const filteredArray = data1.filter(data => IDKeys[data.id]);

This would be only O(n) since accessing key on object is O(1)