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Asynchronous Code Execution works in Node.JS
This blog is a demonstration of how asynchronous code execution in Node.js allows non-blocking operations to be handled efficiently...
console.log('First');
fs.readFile(__filename, () => {
console.log('Second');
});
console.log('Third');Explanation:
1. Initial Execution:
`console.log('First')` is pushed onto the call stack and executed.
The call stack is empty after executing the first `console.log`.
2. Asynchronous Operation (Read File):
`fs.readFile(__filename, () => { console.log('Second'); })` initiates a non-blocking file read operation using the fs module.
The V8 engine hands over the asynchronous operation to `libuv` and continues with the next synchronous operation.
3. Console Output (Synchronous):
`console.log('Third')` is pushed onto the call stack and executed.
The call stack is empty after executing the third `console.log`.
4. Asynchronous Callback Execution:
Once the file read operation is completed, the callback (`() => { console.log('Second'); }`) is pushed into the event queue by `libuv`.
5. Event Loop:
The event loop continuously checks the event queue for any completed asynchronous operations.
6. Callback Execution:
When the event loop detects the callback in the event queue, it's pushed onto the call stack and executed.
`console.log('Second')` is now executed.
7. Console Output (Asynchronous):
The output for 'Second' is printed to the console.
This demonstrates how asynchronous code execution in Node.js allows non-blocking operations to be handled efficiently, allowing the program to continue with other tasks while waiting for asynchronous operations to complete. The event loop and `libuv` play crucial roles in managing these asynchronous tasks.
1. Initial Execution:
`console.log('First')` is pushed onto the call stack and executed.
The call stack is empty after executing the first `console.log`.
2. Asynchronous Operation (Read File):
`fs.readFile(__filename, () => { console.log('Second'); })` initiates a non-blocking file read operation using the fs module.
The V8 engine hands over the asynchronous operation to `libuv` and continues with the next synchronous operation.
3. Console Output (Synchronous):
`console.log('Third')` is pushed onto the call stack and executed.
The call stack is empty after executing the third `console.log`.
4. Asynchronous Callback Execution:
Once the file read operation is completed, the callback (`() => { console.log('Second'); }`) is pushed into the event queue by `libuv`.
5. Event Loop:
The event loop continuously checks the event queue for any completed asynchronous operations.
6. Callback Execution:
When the event loop detects the callback in the event queue, it's pushed onto the call stack and executed.
`console.log('Second')` is now executed.
7. Console Output (Asynchronous):
The output for 'Second' is printed to the console.
This demonstrates how asynchronous code execution in Node.js allows non-blocking operations to be handled efficiently, allowing the program to continue with other tasks while waiting for asynchronous operations to complete. The event loop and `libuv` play crucial roles in managing these asynchronous tasks.