Basics of Promises in JavaScript
A Thread ๐งต
A Thread ๐งต
Q: What are promises in JavaScript?
A: Promises are objects that represent the eventual completion or failure of an asynchronous operation. Promises provide a way to handle success or failure of an asynchronous task without relying on callbacks.
A: Promises are objects that represent the eventual completion or failure of an asynchronous operation. Promises provide a way to handle success or failure of an asynchronous task without relying on callbacks.
Q: How do you create a promise in JavaScript?
A: To create a promise, you can use the Promise constructor, which takes a function with two parameters, resolve and reject.
A: To create a promise, you can use the Promise constructor, which takes a function with two parameters, resolve and reject.
Within this function, you can perform your asynchronous task and then call resolve or reject based on whether the task was successful or not.
Q: How do you use promises in JavaScript?
A: To use a promise, you can call the then method on the promise object to handle the success case, or the catch method to handle the failure case.
A: To use a promise, you can call the then method on the promise object to handle the success case, or the catch method to handle the failure case.
The then method takes a function that is called with the resolved value of the promise, while the catch method takes a function that is called with the reason for the promise's rejection.
Q: How do you chain promises in JavaScript?
A: You can chain promises together using the then method. When you return a value from the then method, it creates a new promise that is resolved with the returned value.
A: You can chain promises together using the then method. When you return a value from the then method, it creates a new promise that is resolved with the returned value.
You can chain multiple then methods to create a sequence of asynchronous tasks that depend on the previous task.
Q: What is Promise.all() in JavaScript?
A: Promise.all() is a method that takes an array of promises and returns a new promise that resolves when all of the input promises have resolved.
A: Promise.all() is a method that takes an array of promises and returns a new promise that resolves when all of the input promises have resolved.
The resolved values of the input promises are returned in an array in the order in which they were passed to the method.
Q: What is Promise.race() in JavaScript?
A: Promise.race() is a method that takes an array of promises and returns a new promise that resolves or rejects as soon as one of the input promises resolves or rejects.
A: Promise.race() is a method that takes an array of promises and returns a new promise that resolves or rejects as soon as one of the input promises resolves or rejects.
The resolved or rejected value of the first input promise is used to resolve or reject the returned promise.
Q: What are some common mistakes to avoid when using promises?
A: One common mistake is to forget to handle errors properly, which can lead to unexpected behavior. Another mistake is to use unnecessary nesting of promises, leading to overly complex and hard-to-read code.
A: One common mistake is to forget to handle errors properly, which can lead to unexpected behavior. Another mistake is to use unnecessary nesting of promises, leading to overly complex and hard-to-read code.
It's important to use appropriate techniques such as chaining and Promise.all() to write maintainable and error-free asynchronous code.
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โก I simplify web development for you in that even a 5-year-old can understand.
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@dun_yan_
โ Retweet and like this post
Thanks for the support ๐
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