Thread by @OzaKaran

🧵Asynchronous JavaScript & Callback🧵

⚡️Informative thread with examples

#100DaysOfCode #CodeNewbie #javascript

Synchronous :

- Synchronous operations in JavaScript entails having each step of an operation waits for the previous step to execute completely.

- This means no matter how long a previous process takes, subsequent process won't kick off until the former is completed.

Asynchronous :

- Asynchronous operations, on the other hand, defers operations.

- Any process that takes a lot of time to process is usually run alongside other synchronous operation and completes in the future.

✨ Callback Function :

- When function simply accepts another function as an argument, this contained function is known as callback function.

- Using callback functions is a core functional programming concept, and you can find them in most JavaScript code; like setInterval

✅ Example - setInterval accepts a callback function as its first parameter and also a time interval. Another example using .map();

✅ In the example above, we used the .map() method to iterate through the array list, the method accepts a callback function which states how each element of the array will be manipulated.

✅Callback functions can also accept arguments as well.

- Callback functions can be named or anonymous functions.

✨ The Given function is assigned a name greeting and has an argument of name. We're also using an ES6 template string. Let’s use this function as a callback function.

- Notice the usage of the callback? The succeeding brackets, () after the function are not used when passing the function as a parameter.

✨Note: The callback function is not run unless called by its containing function, it is called back. Hence, the term call back function

✨Multiple functions can be created independently and used as callback functions.

⚡️These create multi-level functions. When this function tree created becomes too large, the code becomes incomprehensible sometimes and is not easily refactored. This is known as CALLBACK HELL.