How to Count duplicates in array JavaScript?
There are many ways to count duplicates in Array using JavaScript. Like using sorting and for loop or hard-coded elements for each method.
Let’s see HTML example code for it:-
The long way
<!DOCTYPE HTML>
<html>
<body>
<script>
var elements = ["Apple", "Apple", "Orange", "Apple", "Banana"];
elements.sort();
var current = null;
var count = 0;
for(var i = 0; i < elements.length; i++)
{
if(elements[i] != current)
{
if(count > 0)
{
document.write(current + " " + count + "<br/>");
}
current = elements[i];
count = 1;
}
else
{
count++;
}
}
if(count > 0)
{
document.write(current + " " + count);
}
</script>
</body>
</html> The short way
<!DOCTYPE HTML>
<html>
<body>
<script>
var elements = ["Apple", "Apple", "Orange", "Apple", "Banana"];
var counts = {};
elements.forEach(function(x) {
counts[x] = (counts[x] || 0) + 1;
});
document.write("Apple: " + counts.Apple + "<br/>");
document.write("Banana: " + counts.Banana + "<br/>");
document.write("Orange: " + counts.Orange + "<br/>");
</script>
</body>
</html> Output: The result will be the same.
Source: stackoverflow.com
Do comment if you have any doubts or suggestions on this example.
Note: The All JS Examples codes are tested on the Firefox browser and the Chrome browser.
OS: Windows 10
Code: HTML 5 Version