JavaScript Symbol.hasInstance Property

Javascript Web Development Object Oriented Programming

The Symbol.hasInstance property is used to check if a constructor recognizes the object as its instance.

Following is the code for Symbol.hasInstance property −

Example

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
<style>
   body {
      font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
   }
   div {
      font-size: 20px;
      font-weight: 500;
   }
</style>
</head>
<body>
<h1>JavaScript Symbol.hasInstance Property</h1>
<div class="sample"></div>
<button class="Btn">CLICK HERE</button>
<h3> Click on the above button to see if the above symbols are instance of array and custom() respectively</h3>
<script>
   let fillEle = document.querySelector(".sample");
   let ele = [1, 2, 3];
   function custom() {}
   var str = new custom();
   fillEle.innerHTML += ele + "<br>" + custom + "<br>";
   document.querySelector(".Btn").addEventListener("click", () => {
      fillEle.innerHTML += Array[Symbol.hasInstance](ele) + "<br>";
      fillEle.innerHTML += custom[Symbol.hasInstance](str);
   });
</script>
</body>
</html>