Part 31 | JavaScript Tutorial | Callbacks | setInterval and setTimeout in JavaScript | Event Loopin смотреть онлайн

1. Callback functions:-
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- Callback function is a function that is passed as an argument to another function and is executed when that function finishes its execution.

- The purpose of a callback function is to provide a way for a function to asynchronously return a result or execute some code after it has completed.
- In the below example, callBackFunc is function.

function sumValue(x, y, callBackFunc){
//Call the server to get the data from server.
let sum = x + y;

//Once data is received,invoke call back function.
callBackFunc(sum);
}

function printFunc(value) {
console.log(value);
}


1. setTimeout(function, milliseconds)
- If we want to execute any code only one time but after specifying the particular time, then we can use the setTimeout method.

2. setInterval(function, milliseconds)
- If we want to execute any code multiple times based on time interval then we can use the setTimeout method.

3. clearTimeout()
4. clearInterval()

Event looping in JS:-
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JavaScript is a single-threaded language, which means that it can only execute one piece of code at a time. However, it also has a built-in mechanism for handling asynchronous operations, known as the event loop.

The event loop is a continuously running loop that checks for new events in the event queue and processes them one by one. When an asynchronous operation is initiated, such as a setTimeout or a network request, it is added to the event queue and the event loop continues to run. When the operation is completed, a callback function is added to the event queue to be executed in the future.

console.log("start");
console.log("end");

Note that even though the setTimeout function was called with a delay of 0 milliseconds, it still waited until the main thread was finished before executing the callback. This is because it is an asynchronous operation that is queued up by the event loop.