JavaScript Passing parameters to a callback function Last Updated : 09 Jan, 2024 Comments Improve Suggest changes Like Article Like Report Callback FunctionPassing a function to another function or passing a function inside another function is known as a Callback Function. In other words, a callback is an already-defined function that is passed as an argument to the other code Syntax:function geekOne(z) { alert(z); }function geekTwo(a, callback) { callback(a); }prevfn(2, newfn);Above is an example of a callback variable in a JavaScript function. "geekOne" accepts an argument and generates an alert with z as the argument. "geekTwo" accepts an argument and a function. "geekTwo" moves the argument it accepted to the function to pass it to. "geekOne" is the callback function in this case. ApproachIn this, The "GFGexample" is the main function and accepts 2 arguments, and the "callback" is the second one. The logFact function is used as the callback function. When we execute the "GFGexample" function, observe that we are not using parentheses to logFact since it is being passed as an argument. This is because we don't want to run the callback spontaneously, we only need to pass the function to our main function for later execution. Make sure that if the callback function is expecting an argument. Then we supply those arguments while executing. Moreover, you don't need to use the word "callback" as the argument name, JavaScript only needs to know it's the correct argument name. JavaScript callback functions are easy and efficient to use and are of great importance to Web applications and code. Example: This example shows the implementation of the above-explained approach. javascript function GFGexample(fact, callback) { let myFact = "GeeksforGeeks Is Awesome, " + fact; callback(myFact); // 2 } function logFact(fact) { console.log(fact); } GFGexample("Learning is easy since", logFact); OutputGeeksforGeeks Is Awesome, Learning is easy since Comment More infoAdvertise with us Next Article JavaScript Passing parameters to a callback function S ShubhamDodeja Follow Improve Article Tags : JavaScript Web Technologies javascript-functions JavaScript-Questions Similar Reads Passing a function as a parameter in JavaScript In this article, we will pass a function as a parameter in JavaScript. Passing a function as an argument to the function is quite similar to passing a variable as an argument to the function. So variables can be returned from a function. The below examples describe passing a function as a parameter 1 min read JavaScript Function.prototype.call() Method The call() method allows function calls belonging to one object to be assigned and it is called for a different object. It provides a new value of this to the function. The call() method allows you to write a method once and allows it for inheritance in another object, without rewriting the method f 3 min read JavaScript function caller Property The function.caller property of the JavaScript function object returns the function that invoked the specified function. It returns null if the function "f" was invoked by the top-level code in JavaScript. For functions like strict functions, async functions, and generator functions this method retu 2 min read TypeScript Optional Parameters in Callbacks In TypeScript, optional parameters in callbacks are parameters that may or may not be provided when the callback function is invoked. They are denoted by a ? after the parameter name, allowing for more flexible function calls without requiring all arguments.Syntaxtype MyCallback = (param1: string, p 2 min read How to pass a parameter to an event handler or callback ? In React, to pass a parameter to an event handler or callback simply means to execute that function or code when the event is triggered. It links the events to the respective functions. Prerequisites:React JSEvent HandlersReact JS Class ComponentApproachWe will define a function to create a window a 2 min read Like