remove duplicates from array of objects in javascript code example

Example 1: how to remove duplicate array object in javascript

let person = [{name: "john"}, {name: "jane"}, {name: "imelda"}, {name: "john"}];

function removeDuplicates(data, key) {
  
  return [
    ...new Map(data.map(item => [key(item), item])).values()
  ]

};

console.log(removeDuplicates(person, item => item.name));

Example 2: remove duplicate objects from array javascript

const addresses = [...]; // Some array I got from async call

const uniqueAddresses = Array.from(new Set(addresses.map(a => a.id)))
 .map(id => {
   return addresses.find(a => a.id === id)
 })

Example 3: Removing duplicates in an Array of Objects

// BEST ANSWER - LINEAR TIME SOLUTION

const seen = new Set();
const arr = [
  { id: 1, name: "test1" },
  { id: 2, name: "test2" },
  { id: 2, name: "test3" },
  { id: 3, name: "test4" },
  { id: 4, name: "test5" },
  { id: 5, name: "test6" },
  { id: 5, name: "test7" },
  { id: 6, name: "test8" }
];

const filteredArr = arr.filter(el => {
  const duplicate = seen.has(el.id);
  seen.add(el.id);
  return !duplicate;
});

Example 4: how to remove duplicate array object in javascript

var arrayWithDuplicates = [
    {"type":"LICENSE", "licenseNum": "12345", state:"NV"},
    {"type":"LICENSE", "licenseNum": "A7846", state:"CA"},
    {"type":"LICENSE", "licenseNum": "12345", state:"OR"},
    {"type":"LICENSE", "licenseNum": "10849", state:"CA"},
    {"type":"LICENSE", "licenseNum": "B7037", state:"WA"},
    {"type":"LICENSE", "licenseNum": "12345", state:"NM"}
];

function removeDuplicates(originalArray, prop) {
     var newArray = [];
     var lookupObject  = {};

     for(var i in originalArray) {
        lookupObject[originalArray[i][prop]] = originalArray[i];
     }

     for(i in lookupObject) {
         newArray.push(lookupObject[i]);
     }
      return newArray;
 }

var uniqueArray = removeDuplicates(arrayWithDuplicates, "licenseNum");
console.log("uniqueArray is: " + JSON.stringify(uniqueArray));