Passing a Function as a Parameter in JavaScript

Last Updated : 22 Aug, 2026

In JavaScript, functions are first-class objects, which means they can be stored in variables, passed as arguments, and returned from other functions.

  • A function can be passed to another function as an argument.
  • The receiving function can execute the passed function when needed.
  • This makes code more reusable and flexible.
  • This concept is commonly used with callbacks, event handlers, and higher-order functions.

The following approaches demonstrate how to pass a function as a parameter in JavaScript.

Approach 1: Passing a Function Without Arguments

A function can be passed directly as an argument to another function. The receiving function can then call it using ().

JavaScript 
function geeksInner() {
    return "Hello User!";
}

function geeksOuter(func) {
    console.log(func());
}

geeksOuter(geeksInner);

Output
Hello User!
  • geeksInner is passed to geeksOuter without parentheses.
  • func receives the function reference.
  • func() executes the passed function.

Note: Use geeksInner when passing the function. Using geeksInner() would execute the function immediately and pass its returned value instead.

Approach 2: Passing a Function with Arguments

A function can also be passed along with additional arguments. The receiving function can pass those arguments to the callback when it executes it.

JavaScript 
function geeksInner(value) {
    return "Hello " + value;
}

function geeksOuter(value, func) {
    console.log(func(value));
}

geeksOuter("Geeks!", geeksInner);

Output
Hello Geeks!
  • geeksInner accepts the value passed to it.
  • geeksOuter receives both the value and function reference.
  • func(value) executes the passed function with the provided argument.

Approach 3: Passing an Anonymous Function

An anonymous function can be created directly while calling another function and passed as an argument.

JavaScript 
function sayHello(func) {
    console.log("Hello User!");
    func();
}

sayHello(function () {
    console.log("Welcome to GeeksforGeeks!");
});

Output
Hello User!
Welcome to GeeksforGeeks!
  • The anonymous function is passed directly to sayHello().
  • func stores the function reference.
  • func() executes the anonymous function.

Approach 4: Using an Arrow Function

An arrow function can also be passed as a parameter, providing a shorter syntax for callbacks.

JavaScript 
function calculate(a, b, operation) {
    return operation(a, b);
}

const result = calculate(10, 5, (x, y) => x + y);

console.log(result);

Output
15
  • calculate() receives two numbers and a function.
  • The arrow function (x, y) => x + y is passed as the third argument.
  • operation(a, b) executes the passed function.
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