1.Synchronous is just single-threaded thing. Asynchronous is like Multi-threaded thing.
2.A callback hell is when you use a lot of callback functions it is called call back hell.
3.The technnique of “Promise”.
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- What is the difference between synchronous and asynchronous functions?
When running synchronous functions we need to wait to receive the feedback/data of a part of the function before the of the script is executed.
With asynchronous functions, we send a request and the rest of the script is executed, when we receive the data, the function is called back.
- What is callback hell?
Callback hell is when a series of functions and nested functions call for each other.
- Which technique can help us solve callback hell?
To solve callback hell we can use Promises library, or we can extend the runtime to use asynchronous code as if it was synchronous.
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1.) What is the difference between synchronous and asynchronous functions?
Synchronous functions execute one action at a time, and each function must wait for the first to finish. Asynchronous functions multi-task when waiting for a response, so other functions don’t have to wait for the first to finish.
2.) What is callback hell?
When you have an ungodly amount of functions nested inside each other, even to perform simple tasks.
3.) Which technique can help us solve callback hell?
Using promises that come in packs like Meteor, Fiber, jQuery, and others.
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When a synchronous function is called, javascript is completely locked in the completion of the
function code. It can’t perform other tasks till the synchronus function code has been completly
executed.On the other hand when an asynchronous function is called, javascript initializes the function code,
without being locked in till its completion, and go on performing other tasks.
The event loop, working on background, tell the main thread of javascript when all the data required
for the execution of the ascynctounous function code are available.
When this happens javascript will complete the execution of the ascyncronous function. -
Callback hell happens in asynchronous programming when the number of callback handlers
become very high and difficult to manage. -
Javascript can solve the callback hell problem using a jQuery built-in promise library that
allows the programmer to:
a) chain callbacks;
b) deal with errors.
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Synchronous functions execute code in order, one block at a time, while asynchronous functions can run in the background then come back when ready to complete the promised task.
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Callback hell is when several asynchronous operations try to execute simultaneously thereby creating error-prone code that gets hung up.
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JQuery promises uses a built-in library that helps manage callbacks and errors. The Fibers package sub-library called Future makes asynchronous code look synchronous and helps to control flow.
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1 Synchronous functions are executed by Javascript in the order in which they are arranged in the code (from top to bottom) and asynchronous functions are executed only when some programmed condition is reached.
2 Callback hell is an expression designed to indicate the existence of too many nested asynchronous functions.
3 Promises and Generators are the two techniques to solve the callback hell, they can be used separately or together.
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What is the difference between synchronous and asynchronous functions?
The difference between synchronous and asynchronous functions is that a synchronous task will occupy the JS engine continuously until its completion, an asynchronous task can be initiated and then put aside until a later date while other tasks are getting done. -
What is callback hell?
Callback hell is the event of having complex and nested callback functions for simple tasks. -
Which technique can help us solve callback hell?
One technique that helps us deal with excessive callbacks is to use promises. jQuery ships with a simple- built in promise library that enables us to chain callbacks and deal with errors.
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synchronous functions require JS full attention until completed. asynchronous functions give JS more flexibility in how and when the function is completed.
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the compounding of functions and loops on JS that slow or stall the websites functionality
3.we can extend the runtime of the code and actually make it operate and look synchronously instead of asynchronously.
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- A synchronous task will be continuously executed until its completion, an asynchronous task can be initiated and then put aside until a later date while the next task can be started.
- This is a big issue caused by coding with complex nested callbacks. Here, each and every callback takes an argument that is a result of the previous callbacks. In this manner, The code structure looks like a pyramid, making it difficult to read and maintain. Also, if there is an error in one function, then all other functions get affected.
- We can use Promises in order to solve the callback hell. Promises is a technique which uses chains of synchronous functions to act as nested asynchronous functions.
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Synchronous operations block instructions until the task is completed, while asynchronous operations can execute without blocking other operators.
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In computer programming, a callback, also known as a “call-after” function, is any executable code that is passed as an argument to other code that other code that other code is expected to call back (execute) the argument at a given time.
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Promises are used to solve the call back hell situation.
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1.Synchronous functions block the program’s. Asynchronous functions do not block the program.
2. Callback hell is a situation where several functions are being performed in nested form.
3- Promise is used to solve the call back hell situation.
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- Synchronous functions mean that only one section of the code in the function can run at any one time. While in asynchronous functions more than one section of the code in the function can run at any one time.
- Callback hell is a situation when several nested callback functions are needed in order to perform relatively simple tasks. This is undesirable and makes our code harder to write, debug and maintain.
- Promise is used to solve the call back hell situation. jQuery, AngularJS come with promise library. It also handles errors.
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Synchronous functions use full attention of the browser when being executed. You cannot run more than one synchronous functions at once, where as asynchronous functions can be ran and set to the side to be completed later, meaning their execution isn’t of the immediate importance and do not require immediate completion. You can start an asynchronous function then start and complete a synchronous function, then returning to complete the asynchronous function. Asynchronous functions do not lock up the browser while waiting to be completed and are usually in jQuery wrappers.
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Call back hell occurs when creating complex asynchronous functions which contain many other functions within it. These complex webs of functions that follow within one larger function creates what is called callback hell.
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Within jQuery you can use promises. Promises are brought within promise libraries and they allow for you to write asynchronous code in synchronous styled work flow without the code actually being synchronous. Within node.js the same can be done within the fibers package. Fibers can be used to also write asynchronous code with synchronous work flow so that code is easier to read and manage going forward.
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What is the difference between synchronous and asynchronous functions?
synchronous functions must be run one after the other, meaning that the program can not move further until the current function has been completed. This potentially leads to lock ups if a function takes a long time to run. Asynchronous functions can be initiated then completed at a later stage, meaning multiple functions can be running in tandem. -
What is callback hell?
Callback hell is when functions are multi-layered, a function calling on another function and so forth. This produces more levels and sub-levels which quickly becomes very complicated. -
Which technique can help us solve callback hell?
we can use jQuery promises or Node.js Fibers package.
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1. What is the difference between synchronous and asynchronous functions?
Synchronous functions are those who can run one function at one time and other function can’t be started until the first one is finished. That’s why we have also asynchronous functions which can start to run a code and then put a task aside with help of event loop and return to it when it is needed later (by callback) meanwhile running some other functions.
2. What is callback hell?
Callback hell is a term used when there is a lot of complex nested asynchonous functions and therefore it is required a lot of callbacks. And because of its complexity it is called the callback hell.
3. Which technique can help us solve callback hell?
Promises can help us with that. It provides us a possibility to chain callbacks and handle errors.
There is also another option in Node.js and that is Meteor tool and its Fibers package - it helps as to abstract away the asynchonicity and rewrite the code the way it looks synchronous (but in reality it’s asynchronous).
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- The difference is that in synchronous function you can only do one thing,it is single threaded while with asynchronous you can have different tasks without blocking the program.
2.call back hell is a situation where several function performs simultaneously and that means several nested callbacks perform.
3.promise is a solution to the call back hell problem.
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- When you execute something synchronously, you wait for it to finish before moving on to the next task, when you execute something asynchronously, you can move onto the next task before it finishes.
- It is an undesirable situation where several nested callback functions are needed to complete relatively simple tasks. Functions have to wait on callback functions, that are waiting on other callback functions, it gets messy.
- jQuery’s promise library helps for callback hell in the browser, it enables us to chain callbacks and also deal with errors. On Node.js, Fibers are a powerful tool which expose an API to jump between multiple call stacks from within a single thread.
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- Synchronous programming happens one event at time, where as asynchronous programming enables a function to wait while for another time while something else is happening. It is a lot more efficient for complicated systems and functions.
- Callback hell is when you a multitude of levels and sublevels in a complex function.
- A technique to solve callback hell is using promises.
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What is the difference between synchronous and asynchronous functions?
As the name suggests synchronous means to be in a sequence, i.e. every statement of the code gets executed one by one. So, basically a statement has to wait for the earlier statement to get executed.
Asynchronous code allows the program to be executed immediately where the synchronous code will block further execution of the remaining code until it finishes the current one. This may not look like a big problem but when you see it in a bigger picture you realize that it may lead to delaying the User Interface.
What is callback hell?
Callback Hell , also known as Pyramid of Doom, is an anti-pattern seen in code of asynchronous programming. It is a slang term used to describe and unwieldy number of nested “if” statements or functions.
Operations that have more levels and sub levels called Call Back Hell
Which technique can help us solve callback hell?
Write comments.
Split functions into smaller functions.
Using Promises.
Using Async/await.
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1: Synchronous means that the requests are computed one after another.
Asynchronous functions start a request, wait for a feedback from external information, or other conditions needed to fulfill that request, but while waiting it already starts the next request.
2: If to many promises have to be fulfilled. This is caused by a multitude of nested functions
3: Promises and fibers could help manage many callbacks.
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