JavaScript Anonymous Functions

An anonymous function is a function that has no name, hence can’t be called using its name. Anonymous function is assigned and associated with a variable since, in JavaScript, variables can be of type function.

An anonymous function is stored in a variable using an expression defining the function body. The variable holding a function is used as a function name

	var x = function (a, b) {return a * b};

After an anonymous function is stored inside variable, a variable holding a function can be used as normal function call.

<!DOCTYPE html>
<html>
<body>

<p>This example calls a function which performs a calculation, and returns the result:</p>

<p id="demo"></p>

<script>
	var multiply = function (a, b) {return a * b};
	var ans = multiply(25, 7);
document.getElementById("demo").innerHTML = ans;
</script>

</body>
</html>

Download the code Run the code

Advantages of Anonymous functions

Anonymous functions can be passed as arguments to other functions
Recursions and closures are often use Anonymous functions
Anonymous function can be used for scope management as its assigned to variables
jQuery JavaScript library heavily based on Anonymous functions
Anonymous functions gets defined at run-time

Any normal function can be converted to anonymous function with only minor changes.

Normal Function

// calculates square of given number
function calculateSquare(num) {
    return num * num;
}

Anonymous Function

var calculateSquare = function(num) {return num * num;}

Another version of anonymous function

(function() {
    return num * num;
})

Adding a brackets () at the end of above anonymous function will make it self executing

(function() {
    return num * num;
}) ();

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