Filter unique array members (remove duplicates)

METHOD 1 – Using filter:

indexOf will return the first index (position) that a specific value first appear in the array. By checking indexOf(item)=== index, we can get the unique values.

let array = [“🐑”, “😁”, “🐑”, “🐑”, “😁”, “😁”];
const f…


This content originally appeared on DEV Community and was authored by KenjiGoh

METHOD 1 - Using filter:

indexOf will return the first index (position) that a specific value first appear in the array. By checking indexOf(item)=== index, we can get the unique values.

let array = ["🐑", "😁", "🐑", "🐑", "😁", "😁"];
const filterArr = array.filter((item, index) => array.indexOf(item) === index);
console.log(filterArr); //[ '🐑', '😁' ]

Instead of checking for duplicates using array.filter() method, we can make use of the Set Data Structure that by definition only allows unique values.

METHOD 2 - Using Set: 

const unique = (arr) => {
  const nameSet = new Set();
  for (let i = 0; i < arr.length; i++) {
    nameSet.add(arr[i]); //add element to Set
  }
  Array.from(nameSet)
};
console.log(unique(values)); //[ '🐑', '😁' ]

Shorter Method 

const unique = (arr) => {
   return Array.from(new Set(arr));
}

Set with Array Destructuring 

const unique = (arr) => {
   return [...new Set(arr];
}

METHOD 3 - Using Reduce: 

const uniqueVal = array.reduce((unique, item) =>
  unique.includes(item) ? unique : [...unique, item]
);

console.log(uniqueVal); //[ '🐑', '😁' ]


This content originally appeared on DEV Community and was authored by KenjiGoh


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