js filter array for unique values code example
Example 1: javascript get distinct values from array
const categories = ['General', 'Exotic', 'Extreme', 'Extreme', 'General' ,'Water', 'Extreme']
.filter((value, index, categoryArray) => categoryArray.indexOf(value) === index);
This will return an array that has the unique category names
['General', 'Exotic', 'Extreme', 'Water']
Example 2: javascript remove uniques from array
function getNotUnique(array) {
var map = new Map();
array.forEach(a => map.set(a, (map.get(a) || 0) + 1));
return array.filter(a => map.get(a) > 1);
}
console.log(getNotUnique([1, 2, 2, 4, 4]));
console.log(getNotUnique([1, 2, 3] ));