The JavaScript eval() is used to execute an argument. The code gets execute slower when the eval() method is used. It also has security implementations since it has a different scope of execution. In addition, use it to evaluate a string as a JavaScript expression.
The eval() method is not suggested to use in JavaScript since it executes slower and improper usage opens your website to injection attacks.
Example
Here’s how you can implement eval() function
Live Demo
<html>
<body>
<script>
var a = 30;
var b = 12;
var res1 = eval("a * b") + "<br>";
var res2 = eval("5 + 10") + "<br>";
document.write(res1);
document.write(res2);
</script>
</body>
</html>