Strict equality vs Loose equality in JavaScript.

Javascript Web Development Object Oriented Programming

The loose equality operator ‘==’ allows us to compare two or more operands by converting their value to a common type first and then checking for the equality between them.

strict equality operator ‘===’ allows us to compare two or more operands by checking the equality between the values as well as their types . It returns true only if the values and the type both match with the other operand.

Following is the code for loose equality vs strict equality in JavaScript −

Example

Live Demo

<!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;
   }
   .result {
      font-size: 20px;
      font-weight: 500;
      color: blueviolet;
   }
</style>
</head>
<body>
<h1>Strict equality vs Loose equality</h1>
<div class="result"></div>
<br />
<button class="Btn">CLICK HERE</button>
<h3>Click on the above button see some comparisons using loose equality and strict equality</h3>
<script>
   let resEle = document.querySelector(".result");
   let BtnEle = document.querySelector(".Btn");
   BtnEle.addEventListener("click", () => {
      resEle.innerHTML = "According to loose equality <br>";
      if (1 == "1") {
         resEle.innerHTML += "1 is equal to '1'<br>";
      }
      if (undefined == null) {
         resEle.innerHTML += "undefined is equal to null <br>";
      }
      resEle.innerHTML += "<br>According to strict equality <br>";
      if (1 === "1") {
         resEle.innerHTML += "1 is equal to '1'<br>";
      } else {
         resEle.innerHTML += "1 is not equal to '1'<br>";
      }
      if (undefined === null) {
         resEle.innerHTML += "undefined is equal to null <br>";
      } else {
         resEle.innerHTML += "undefined is not equal to null <br>";
      }
   });
</script>
</body>
</html>