如何从 React Native 中未定义键值的数组中删除 object？

Question

I have a list which after selecting values returns an array. Now, suppose I select 1st and 3rd values skipping 2nd one then the array returned is as:

 [
  {
   "cname": "10TKN", 
   "code": "403", 
   "id": 1
  },
  {
   "cname": undefined, 
   "code": undefined, 
   "id": 2
  }, 
  {
   "cname": "20TKN", 
   "code": "403", 
   "id": 3
  }
 ]

I want the expected result as:

 [
   {
    "cname": "10TKN", 
    "code": "403", 
    "id": 1
   },
   {
    "cname": "20TKN", 
    "code": "403", 
    "id": 3
   }
 ]

Answer 1

You can use JavaScript's Array.filter() to filter away undefined values.

 const data = [ { "cname": "10TKN", "code": "403", "id": 1 }, { "cname": undefined, "code": undefined, "id": 2 }, { "cname": "20TKN", "code": "403", "id": 3 } ]; const res = data.filter(({cname, code, id }) => cname && code && id); console.log(res);

This will ensure that only objects with truthy values are returned.

Alternatively, as mentioned by HMR on the comments, if you only want to check for undefined , it will be better to do this:

const res = data.filter(({cname, code, id }) => cname !== undefined && code !== undefined && id !== undefined);

Answer 2

Assuming the key that we want to evaluate is cname . We need to filter out the array using Array.filter function -:

 let arr = [ { "cname": "10TKN", "code": "403", "id": 1 }, { "cname": undefined, "code": undefined, "id": 2 }, { "cname": "20TKN", "code": "403", "id": 3 } ]; arr = arr.filter(({cname}) => cname); console.log(arr)

Answer 3

You can use filter as suggested already but you will have to check for the selected id(s) from list and then discard the ones not selected. In short you will return true only if the list object id matches with the one you selected

const dataList = [
  {
   "cname": "10TKN", 
   "code": "403", 
   "id": 1
  },
  {
   "cname": undefined, 
   "code": undefined, 
   "id": 2
  }, 
  {
   "cname": "20TKN", 
   "code": "403", 
   "id": 3
  }
 ];

 const selectedDataIds = [1, 3];
 const res = dataList.filter(({ id }) => selectedDataIds.includes(id));
 console.log(res);

Answer 4

You can use Destructuring assignment and skip some values with a comma, like this:

 const arr = [ { "cname": "10TKN", "code": "403", "id": 1 }, { "cname": undefined, "code": undefined, "id": 2 }, { "cname": "20TKN", "code": "403", "id": 3 } ] const [first, ,third] = arr; console.log(first, third);

Destructuring assignment - Ignoring some returned values