JavaScript - how to get unique objects

In this article, we would like to show you how in JavaScript find unique objects in the array.

Below example presents how to create a function that returns unique objects using:

• locks object to store unique object as JSON,
• valueGetter that creates normalized JSON objects located in the array.

Note:

As normalized JSON we understand JSON with ordered properties - below example, we take care of properties order.

Practical example:

// ONLINE-RUNNER:browser;

const getUniqueItems = (items, valueGetter) => {
const locks = {};
  const result = [];
  for (const item of items) {
      const value = valueGetter(item);
    if (value in locks) {
          continue;
       }
       locks[value] = true;
       result.push(item);
   }
  return result;
};

// Usage example:

const items = [
 {name: 'john',  age: 20},
 {name: 'anna',  age: 25},
 {age: 20, name: 'john'},
];

const valueGetter = (item) => JSON.stringify({name: item.name, age: item.age});
const uniqueItems = getUniqueItems(items, valueGetter);

console.log(JSON.stringify(uniqueItems, null, 4));

Note:

We must remember to create the valueGetter function ourselves or provide a generic function.

Related posts

• JavaScript - convert object to JSON with ordered properties