remove duplicate numbers in array js code example

Example 1: js delete duplicates from array

const names = ['John', 'Paul', 'George', 'Ringo', 'John'];

let unique = [...new Set(names)];
console.log(unique); // 'John', 'Paul', 'George', 'Ringo'

Example 2: remove duplicates array javascript

var data = [1, 2, 'Peter', 3, 3,'Peter', 2, 2, 1, 2, 3, 4, 4, 5, 4];
var unique = data.filter((v, i, a) => a.indexOf(v) === i);

Example 3: remove duplicates from array javascript

function onlyUnique(value, index, self) {
  return self.indexOf(value) === index;
}

// usage example:
var a = ['a', 1, 'a', 2, '1'];
var unique = a.filter(onlyUnique);

console.log(unique); // ['a', 1, 2, '1']

Example 4: remove duplicates array javascript

function uniqByKeepFirst(a, key) {
    let seen = new Set();
    return a.filter(item => {
        let k = key(item);
        return seen.has(k) ? false : seen.add(k);
    });
}


function uniqByKeepLast(a, key) {
    return [
        ...new Map(
            a.map(x => [key(x), x])
        ).values()
    ]
}

//

data = [
    {a:1, u:1},
    {a:2, u:2},
    {a:3, u:3},
    {a:4, u:1},
    {a:5, u:2},
    {a:6, u:3},
];

console.log(uniqByKeepFirst(data, it => it.u))
console.log(uniqByKeepLast(data, it => it.u))

Example 5: javascript remove duplicates from array

let chars = ['A', 'B', 'A', 'C', 'B'];
let uniqueChars = [...new Set(chars)];

console.log(uniqueChars);
Code language: JavaScript (javascript)