javascript unique array of objects by property code example

Example 1: javascript map return array with distinc values

//ES6
let array = [
  { "name": "Joe", "age": 17 },
  { "name": "Bob", "age": 17 },
  { "name": "Carl", "age": 35 }
];
array.map(item => item.age)
  .filter((value, index, self) => self.indexOf(value) === index)

> [17, 35]

Example 2: javascript unique array of objects by property

const array =
  [
    { "name": "Joe", "age": 17 },
    { "name": "Bob", "age": 17 },
    { "name": "Carl", "age": 35 }
  ]

function uniqueByKey(array, key) {
  return [...new Map(array.map((x) => [x[key], x])).values()];
}

console.log(uniqueByKey(array, 'age'));

Example 3: javascript get unique values from key

const unique = [...new Set(array.map(item => item.age))];

Example 4: javascript find unique values in array of objects

var flags = [], output = [], l = array.length, i;
for( i=0; i<l; i++) {
    if( flags[array[i].age]) continue;
    flags[array[i].age] = true;
    output.push(array[i].age);
}