Callbacks and Callback Hell
Callback is a built-in function in JavaScript programming, which is used to pass an argument to another function in an argument order format in JavaScript programming. After this, when the callback seconds and the remaining function related task is completed, or executed. Currently, in modern JavaScript programming, callback function is used for asynchronous programming operations such as reading files from the system, making requests from the client or web network, or controlling and managing user interaction in the system.
Example of JavaScript callback function.
Callback function in JavaScript programming.
function employee(emp_name, callback) {
console.log(‘Employee name is – ‘ + emp_name);
callback(); // let here it used to Calling the callback function in active program
}
function callbackFunc() {
console.log(‘Let tests the callback function.’);
}
employee(‘Harry’, callbackFunc);
In JavaScript callback function example.
In this callback program, the employee() function is declared and input as parameters an employee name and a callback function.
After the employee is displayed as the employee name, the callback function is executed in the program.
Callback functions are essential for modern JavaScript asynchronous programming. As such, callback functions can often be used in grouping with built-in functions like setTimeout(), setInterval() or asynchronous APIs like fetch() function in modern advanced JavaScript programming.
JavaScript Callback Hell Function.
Callback hell is a built-in function in modern JavaScript programming, also known as destruction in JavaScript, callback hell refers to some particular condition. Where callback functions are nested inside other callback functions like nested functions, which makes the existing program source code deeply indented and complicated to read. Generally, this operation is performed when an existing program has to deal with multiple callback hell asynchronous operations that are dependent on each other, especially in conditions where the programmer needs to execute multiple programming tasks one after the other.
Example of JavaScript callback hell.
function taskone(callback) {
setTimeout(() => {
console.log(“here first task is completed”);
callback();
}, 1000); // lets set 1 millisecond time interval for first callback
}
function tasktwo(callback) {
setTimeout(() => {
console.log(“here second task is completed”);
callback();
}, 2000);
}
function taskthree(callback) {
setTimeout(() => {
console.log(“here three task is completed”);
callback();
}, 3000);
}
function tasktfourth(callback) {
setTimeout(() => {
console.log(“here fourth task is completed”);
callback();
}, 4000);
}
// let set Callback Hell situation with Nested callbacks condition
taskone(() => {
tasktwo(() => {
taskthree(() => {
tasktfourth(() => {
console.log(“All callback tasks completed yet now”);
});
});
});
});
Callback Hell Function in example.
Here, in the callback hell function program, taskone, tasktwo, taskthree, and tasktfourth are asynchronous programming callback tasks, all of which are executed in sequence in one-by-one order.
Whereas each function task depends on the completion of the previous task, hence the callbacks are run one by one in nested order.
As more tasks are added to an existing function program, the program indentation behaviour becomes deeper, making it difficult to read and maintain the existing program source code.
Why is callback hell problematic in JavaScript?
- Program readability – Callback hell causes JavaScript programs to be deeply nested, making it difficult to read and understand the callback functions in the existing program.
- Program maintainability – As the program source code increases with callback functions, it becomes more complex to modify the existing callback program capability or add new functions.
- Program error handling – Managing and controlling errors in deeply nested program source code with large existing callbacks becomes more complex.
- Program debugging – When callbacks are deeply nested in a program source code, manually debugging existing callback asynchronous program source code becomes more complex, especially when programmers are dealing with many program tasks or events in a program.
Summary of JavaScript Callbacks & Callback Hell.
- Callback functions – JavaScript programs have functions that are passed as arguments to another program function to execute later, typically in order to manage or handle asynchronous programming tasks.
- Callback Hell Function – Callback Hell functions occur in JavaScript programs when callback functions are declared nested inside other callback functions. This makes reading the existing program source code and maintaining the program a bit complex.
