Asynchronous Programming - Reading Assignment

[realsloth]

1. Synchronous functions tun one after the other in a single thread. Asynchronous functions can run together at the same time without pausing the execution until one function is done.
2. Asynchronous functions can apparently clog the server.
3. Using Fibers from the Future sub-library allows you to build a synchronous equivalent to asynchronous functions.

[YYZ10]

1. Synchronous functions need to be executed one at a time with no interruption before moving into the next task. Asynchronous functions allow for other work to be done.
2. When nested callback functions are needed to complete tasks. They are more difficult to write.
3. Promises can to used to solve the problem.

[sherlock]

1. Synchronous functions are blocking javaSript until their task is finished whereas asynchronous functions executing other tasks while the previous tasks havent finished yet.

2. Several nested functions.

3. Promise library that enables us to chain callbacks and deal with errors.

[cw82para]

1. Synchronous each statement waits for the previous one to be done before executing. Asynchronous code does not have to wait and continues to run eliminating delays.

2. Multiple nested callbacks.

3. Promises

[dragos_andrei_87]

1. What is the difference between synchronous and asynchronous functions?

• Synchronous code will run in an ordered way top to bottom. It will execute a code line and after it will pass to the next code line.
• Asynchronous code can start something now and finish it later, basically it will run “randomly”.

2. What is callback hell?

• When using multiple asynchronous code/functions and we are not careful with the way we structure the callbacks, it will become hard to work with and understand the code.
• We will have a callback within a callback within a callback…etc, make it very difficult to understand it and debug it.
  
  

3. Which technique can help us solve callback hell?

• We can use the processes called PROMISES.
• Promises is an object/process that represents an action that hasn’t finished yet, but will do at some point down the line.
• Promises are placeholders for asynchronous operations.

More details you can find in the video tutorials bellow.

[JanjoHR1]

• What is the difference between synchronous and asynchronous functions?

• Sync. functions allow us to do only one function at the time, it is single threaded, while async. functions allows us to start something and if we put it aside it won’t occupy the whole javascript, but rather it will continue to perform normally with other tasks.
  
  

• What is callback hell?

• Callback hell is when we have more nested functions that usually wait for some event to happen to be executed and this causes more levels and sub levels, and in this way it makes the operations more complex.
  
  

• Which technique can help us solve callback hell?

• In the browser t is a built in library called promise
  But in Node.js, byextending the runtime, we can abstract away the
  asynchronicity and write code that looks sychronous.

[jon_m]

Hi @realsloth,

Just to clarify…

@realsloth

2. Asynchronous functions can apparently clog the server.

The term callback hell refers to readability and manageability of asynchronous functions, rather than about how efficiently they execute.

Callback hell descibes code that uses multiple levels of nested callback functions (often referred to as the pyramid of doom ) to perform a complex set of asynchronous operations with interdependent inputs and outputs. This approach often results in dense and convoluted code with a confusing control flow, which is therefore difficult to read, debug and develop further.

@realsloth

3. Using Fibers from the Future sub-library allows you to build a synchronous equivalent to asynchronous functions.

… and using JavaScript promises can also help us solve callback hell.

[jon_m]

Hi @YYZ10,

Just to clarify…

@YYZ10

2. When nested callback functions are needed to complete tasks. They are more difficult to write.

The term callback hell refers more to readability and manageability of asynchronous functions, rather than how difficult they are to write.

When multiple levels of nested callback functions are written to perform a complex set of asynchronous operations with interdependent inputs and outputs, this often results in dense and convoluted code with a confusing control flow, which is therefore difficult to read, debug and develop further.

[jon_m]

Hi @sherlock,

Just to clarify…

@sherlock

3. Promise library that enables us to chain callbacks and deal with errors.

Yes … JavaScript promises can help us solve callback hell. But they don’t involve chaining callbacks, becuse they don’t need to use callback parameters for success and error handling. Instead they enable success and error handling to be managed and performed using chained .then() and .catch() methods . This chaining of operations results in code with a synchronous style of control flow .

[Matoshi]

1. For synchronous function it is mandatory to finish first function completely, before starting to execute the second function. Asynchronous functions allows to start one function and somewhere in between to execute the second, third function and so on.

2. In complex programs exist a lot of levels and sub levels of asynchronous functions waiting a nested callback and to be executed and all that mess is called a callback hell.

3. One of the way to deal with is promises supported by built in Library, another way is to use Fibers of Node.js.

[Katoch]

1. What is the difference between synchronous and asynchronous functions?
   Synchronous functions executes runs one at a time,
   whilst asynchronous functions can be used to execute multiple lines of code in a moment.
2. What is callback hell?
   It is when callbacks are within each other, I can strongly say that Inception was inspired by callback hell.
3. Which technique can help us solve callback hell?
   “Promises” are used to solve callback hell situations.

[Nityam_Jigyasu]

1. Synchronous code is executed in sequence – each statement waits for the previous statement to finish before executing. Asynchronous code doesn’t have to wait – your program can continue to run. You do this to keep your site or app responsive, reducing waiting time for the user.
2. Callback hell is any code where the use of function in async code becomes obscure or difficult to follow. Generally, when there is more than one level of indirection, code using callbacks can become harder to follow, harder to refactor, and harder to test.
3. Use of “Promises”, which enables us to chain callbacks, write async code and deal with errors. jQuery, AngularJS come with promise library and Meteor does it via Fibers package.

[Long]

@ivan

• What is the difference between synchronous and asynchronous functions?
• What is callback hell?
• Which technique can help us solve callback hell?

1. synchronous functions = happen one after another and prevents the next function to begin executing until the previous one has completed. Asynchronous functions WILL allow other functions to start executing before it has completed all its tasks.
2. complexity in code causing a situation where several functions are being performed in nested form.
3. Promises via jQuery library.

[Mucha_Julius]

1. Synchronous functions are those that are ‘blocking’ that is to say that they occupy the Javascript engine until their execution is finished. Asynchronous function on the other hand do not block the Javascript thread, instead they wait for execution to complete while the thread does other work.

2. Callback hell is an undesirable situation whereby several nested callback functions are needed in order to perform relatively simple tasks

3. We can use promises to solve the problem of call back hell.

[LaszloD]

1. What is the difference between synchronous and asynchronous functions?
   In synchronous functions only one piece of code can run at any one time, so task n+1 has to wait till task n is finished before it can run. With asynchronous functions, the code can go on executing more tasks while waiting for a call to complete in the background. The event loop schedules calls automatically in a stack (synchronous) and a queue (asynchronous).
2. What is callback hell?
   Chaining many callback functions together in what quickly becomes very messy code.
3. Which technique can help us solve callback hell?
   Promises (a kind of object) on the client side, and this Fibers library.

[daz3d]

What is the difference between synchronous and asynchronous functions?

1. Synchronous In a single threaded environment instructions are executed one after the other. Only one task can be performed at a time. This is known as blocking or synchronous. It cause the browser to lock up until the previous task is completed.
2. Asynchronous is also a single threaded environment but is different from synchronous in the sense that each command is executed one after the other but the difference being if more time is needed for completion of a task the response can be deferred until the task is complete allowing the flow control to continue without locking up the computer.

What is callback hell?

In asynchronous programming nested levels of arguments are tied together to respond to tasks. Some times these nested levels and be 3 or more levels deep and this situation leads to what is known as call back hell.

Which technique can help us solve callback hell?

Promises were introduced to allow for asynchronous programming. jQuery has a built in library to simplify coding promises but you can also use javascript. After having a look at javascript handling of promises jQuery does look a lot easier to use. Also in node.js the package meteor uses a package fibers which deals with promises but also makes the code simple and look synchronous.

[jon_m]

Hey @LaszloD,

Nice answers

@LaszloD

2. What is callback hell?
   Chaining many callback functions together …

I think what you mean is nesting.

Chaining is what we do in promises, using chained .then() and .catch() methods. This chaining of operations results in code with a synchronous style of control flow, which has a much clearer control flow than multiple layers of convoluted callback functions. Using promises results in code which is easier to read, debug and develop further, and enables a clearer management of success and error handling.

[jon_m]

Great explanations @daz3d!

[LaszloD]

Yes, nesting is the correct term, sorry. Nesting callbacks reminds a lot of recursion.

[lfsvamaral]

1. What is the difference between synchronous and asynchronous functions?

Synchronous functions waits for each operation to complete and only when an operation is finished it will execute the following operations. Asynchronous functions on the other hand can start multiple operations at the same time and wait for their completation while executing other operations.

2. What is callback hell?

Callback hell is used to describe when we have multiple nested callback functions, potentially making it more difficult to understand and maintain the code.

3. Which technique can help us solve callback hell?

Using Promise library in jQuery enables us to chain callbacks and deal with errors. We can also extend runtime in Node.js allowing us to abstract away the asynchronicity and write code that looks sychronous.