JavaScript Set contains

Use set has() method to check specified value Set contains or not in JavaScript. It returns true if the specified value is present, otherwise false.

setObj.has(value)

JavaScript Set contains

A simple example code set has JavaScript.

<!DOCTYPE html>
<html>
<body>

  <script>
   const set1 = new Set([1, 2, 3, 4, 5]);

   console.log(set1.has(1));

   console.log(set1.has(5));

   console.log(set1.has(6));
 </script>
</body>
</html>

Output:

More examples

const mySet = new Set();
mySet.add('foo');

mySet.has('foo');  // returns true
mySet.has('bar');  // returns false

const set1 = new Set();
const obj1 = {'key1': 1};
set1.add(obj1);

set1.has(obj1);        // returns true
set1.has({'key1': 1}); // returns false because they are different object references
set1.add({'key1': 1}); // now set1 contains 2 entries

Checking if a Set contains a list in JavaScript

You can’t compare references like arrays and objects for equality (you can compare values, though).

The way you’re doing it, you’re checking against a different reference, even though the values appear to be the same.

Do something like this:

var a = new Set();
var b = [1];

a.add(b);

a.has(b); // => true

Do comment if you have any doubts or suggestions on this Js set topic.

Note: The All JS Examples codes are tested on the Firefox browser and the Chrome browser.
OS: Windows 10
Code: HTML 5 Version

JavaScript Set contains | Example