Use Object.values() and reduce() methods to return a new array of objects to count duplicates in an array of objects. Another way in JavaScript is to use Map and spread syntax …
JavaScript count duplicates in an Array of objects Example
HTML example code
Using Reduce method
<!DOCTYPE HTML>
<html>
<body>
<script>
const array = [ { x: 1, y: 2 }, { x: 3, y: 4 }, { x: 1, y: 2 }, { x: 3, y: 4 }, { x: 1, y: 2 }, { x: 3, y: 12 } ]
const result = Object.values(array.reduce((r, e) => {
let k = `${e.x}|${e.y}`;
if(!r[k]) r[k] = {...e, count: 1}
else r[k].count += 1;
return r;
}, {}))
console.log(result)
</script>
</body>
</html> Output:
Using Map and spread syntax …
const array = [ { x: 1, y: 2 }, { x: 3, y: 4 }, { x: 1, y: 2 }, { x: 3, y: 4 }, { x: 1, y: 2 }, { x: 3, y: 12 } ]
const result = [...array.reduce((r, e) => {
let k = `${e.x}|${e.y}`;
if(!r.has(k)) r.set(k, {...e, count: 1})
else r.get(k).count++
return r;
}, new Map).values()]
console.log(result)Do comment if you have any doubts and suggestions on this JS Array Object topic.
Note: The All JS Examples codes are tested on the Firefox browser and the Chrome browser.
OS: Windows 10
Code: HTML 5 Version