Concept of Callback Functions in JavaScript

Higher-order function is a concept where a function, like string or array, is passed as a parameter into another JS function in form of an argument. A callback function is one of the frequently used programming techniques that can easily pass the regular variables as an argument. These are first-class objects that are called or returned by other functions and are executed later.

Using Callback function in JavaScript with an example -

When callback functions are called in the form of variables and returned in another function, only function definition is passed. Moreover, a function will not be called immediately but only at the fixed point inside the function’s body. There are some functions which can also be accessed later via the argument object in the containing function.

Implementation of the Callback Functions:

• When a callback function is passed in form of argument into some other function, then such functions can access the variables from the global scope which means a callback function is a type of closure. However, a closure is a combination of functions used to access the function’s scope. This further allows the callback function to access the function’s variables from the global scope.
• An anonymous function in JavaScript allows the programmers to create function which has no name. These also store the functionality in variables as a callback function. It is the most common pattern of using the Callback function.
• By using the callback functions, a programmer can also pass parameters to it. A passed function’s property can be anything like a global or local variable.
• The use of “Call” or “Apply” function is helpful in setting this object and correctly executing the callback function. It easily sets the object inside the function and passes arguments to it.

Using higher-order functions is an important way to make the coding, easy to understand and maintain. It is the only technique to combine different functions with each other. As JavaScript concepts are quite hard to understand, it’s better to practice on more and more coding. CodeFights is an effective platform for practicing complex scripts and also prepare for the technical interviews.

The author of this article is a programming enthusiast who regularly writes useful content for the learners to easily understand the JavaScript ideas. You must keep watching this space to remain updated with all new JS approaches.