The change method is a Jquery Event Method. It is an inbuilt method occurs when the value of an input field has been changed  (only works on <input>, <textarea> and <select> elements)The change() method triggers the change event, or attaches a function to run when a change event occurs.

Syntax
$(selector).change() -Trigger the change event for the selected elements.

$(selector).change(function) - Attach a function to the change event.

Example

<html> 

<head> 
	<script src="https://ajax.googleapis.com/ajax/libs/ 
			jquery/3.3.1/jquery.min.js"></script> 
	<!--Demo of change method without passing function-->
	<script> 
		$(document).ready(function() { 
			$("button").click(function() { 
				$("input").change(); 
			}); 
		}); 
	</script> 
</head> 

<body> 
	<p>Click the button to see the changed value !!!</p> 
	<!--click on this button and see the change -->
	<button>Click Me!</button> 
	<p>Enter value: 
		<input value="Donald" onchange="alert(this.value)"
		type="text"></p> 
</body> 

</html>