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Title: Understanding Callback Functions in Javascript
As a developer, it is very common to come across the term “callback” while dealing with Javascript functions. Callbacks are essential for asynchronous programming and can help in running code after an asynchronous operation has completed. In this article, we will deep dive into what exactly a callback function is and how it works in Javascript.
What is a Callback Function?
A callback function is a function that is passed as an argument to another function and is executed after the completion of some operation. The function that takes the callback function as an argument is often referred to as a higher-order function.
One of the most common examples of callback functions is the `setTimeout` function. This function takes two arguments, a function or a code snippet, and a time delay in milliseconds. Once the delay is over, the function will execute the code that was passed as an argument to `setTimeout`. Here’s an example:
“`
setTimeout(function(){
console.log(“Hello World!”);
}, 2000);
“`
In this example, `setTimeout` is passed a function that logs “Hello World!” in the console after a delay of two seconds. Once the delay is over, the function is executed, and the output will be printed in the console.
How Callback Functions Work?
To understand how callback functions work, let’s take a look at the following example:
“`
function add(num1, num2, callback) {
var sum = num1 + num2;
callback(sum);
}
function displayResult(result) {
console.log(result);
}
add(5, 10, displayResult);
“`
In this example, we have two functions: `add` and `displayResult`. `add` takes in two numbers, adds them together, and then executes the callback function that was passed as an argument. In this case, the `displayResult` function was passed as a callback to `add`.
When `add` is executed, it adds `num1` and `num2` together and then immediately executes the callback function `callback(sum)`. The `displayResult` function passed as a parameter to `add` is executed as a result, and the output ’15’ is displayed in the console.
Conclusion
Callback functions are a crucial concept in Javascript, and they help in executing code after an asynchronous operation has completed. Understanding the basics of callbacks goes a long way in writing clean, efficient, and maintainable code using Javascript.
In conclusion, callback functions are an essential tool in the Javascript developer’s toolkit. Their mastery can help in ensuring that your code is robust and efficient, and they are the backbone of asynchronous programming in Javascript. With this knowledge, you can start creating more complex Javascript applications and take advantage of the various tools available to you. Happy coding!
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