how to remove first element of duplicate in an array of objects-CodePudding

pardon my English , i want to remove first element of an array of object if it occur twice

here is the array=[{id:34,value:45}, {id:23,value:35}, {id:34,value:28}]

i want to remove first element because third element's id is same as first element

output should be array=[{id:23,value:35}, {id:34,value:28}]

CodePudding user response：

This will give you an array with the last value for duplicated elements, in preserved order. If you want exactly the 2nd one you need an extra flag

array=[{id:34,value:45}, {id:23,value:35}, {id:34,value:28}]




const obj = array.reduce ( (acc,cur,index) => {
  acc[cur.id] = {index:cur};
  return acc;
},{});

const output = Object.values(obj).sort( (a,b) => a.index - b.index).map( ({index:val}) => val )

console.log(output)

CodePudding user response：

A solution using ES6

const array = [
  { id: 34, value: 45 },
  { id: 23, value: 35 },
  { id: 34, value: 28 },
];

const convertToArray = array.map(({ id, value }) => [id, value]);
const convertToSet = Object.fromEntries(convertToArray);
const revertAsCleanedArray = Object.entries(convertToSet);
const cleanedArrayOfObjects = revertAsCleanedArray.map(([id, value]) => ({id, value}));

CodePudding user response：

Get all unique values in a JavaScript array

let arr = [{id:34,value:45}, {id:23,value:35}, {id:34,value:28}]
var unique = arr.reverse().filter((v, i, a) => a.map(e => e.id).indexOf(v.id) === i);
console.log(unique);

CodePudding user response：

This can help you

let array = [{id:34,value:45}, {id:23,value:35}, {id:34,value:28}]

let result = array.filter((x,i) => array.findLastIndex(y => y.id == x.id) == i)

console.log(result)