remove duplicates in javascript without in built function code example

Example 1: javascript filter array remove duplicates

// Using the Set constructor and the spread syntax:

arrayWithOnlyUniques = [...new Set(arrayWithDuplicates)]

Example 2: remove duplicates strig javascript

const arr = [1, 2, [3, 4]];

// To flat single level array
arr.flat();
// is equivalent to
arr.reduce((acc, val) => acc.concat(val), []);
// [1, 2, 3, 4]

// or with decomposition syntax
const flattened = arr => [].concat(...arr);