Reject chỉ xảy ra nếu request không thể hoàn thành, ví dụ một lỗi mạng. Include an action, the API’s URL, and then send the request as a method. Once you have it, you can initialize a request. It included a quick tutorial on how to use both of them and points out their main differences. If you want to know more about prototypes, check out Prototype. It returns a promise with the response body as JSON. Nó thường được xử lý với response.ok được đặt thành false. Yes, there is.
Another important property is the json function. All rights reserved. Vậy tại sao không sử dụng nó thay vì XMLHttpRequest? The XMLHttpRequest is the old and traditional way to make HTTP requests, fetch () is a modern one which returns a promise. Fetch API tương đối mới, nó không cung cấp tất cả chức năng XHR và một số tùy chọn rất cồng kềnh. Is there a cleaner way to make requests?
Các interface về Headers , Request , Response được cung cấp một cách nhất quán, Promises cho phép xâu chuỗi một cách dễ dàng hơn và async/await không có callback . Fetch API is a new standard allowing you to make network requests in a similar manner to the XHR. Despite its name, XHR can be used to fetch data in a form other than XML: JSON, HTML or plain text. An introduction to multithreading in the browser. Nowadays, JavaScript is often used to make Ajax requests. It differs from the relatively new Fetch API that was introduced a few years ago. I wondered (internally, of course, I didn’t want to lose face in front of the tech-bros) how many years of experience I would need to write that kind of code.
Fetch was introduced as an improvement to XMLHttpRequest and although it is not yet supported by all browsers, it has made making requests easier.
Ultimately, the choice is yours … unless your application has IE clients who demand upload progress bars. Ngoài ra những phiên bản của Chrome, Firefox và Safari cũ hơn 2017 có thể gặp vấn đề. According to the MDN: The Promise returned from fetch() won’t reject on HTTP error status even if the response is an HTTP 404 or 500. Không giống như XMLHttpRequest, không phải tất cả các cài đặt Fetch sẽ gửi cookie để xác thực và ứng dụng của bạn có thể thất bại. Do đó không thể báo cáo trạng thái tệp tải lên hoặc gửi form lớn. API is an acronym for Application Program Interface and it is a means (interface) through which two or more software communicate. I choose the simplicity of fetch() for my requests, how about you? Ví dụ XHR ở trên có thể được chuyển đổi thành Fetch-based code đơn giản hơn nhiều. Unfortunately, so will Fetch once you start to consider the complexities of timeouts, call aborts, and error trapping. It has a set of properties that you can use to further handle the response of your request. An unsent request status is 0 while a completed request status is 200. The four actions an API can take include: Is it too long to understand?
Even though people used some tricks to create sites that fetch additional data before XMLHttpRequest, the introduction of XHR was quite a milestone in the history of web development. The first time I heard the term API as a beginner, it sounded like something huge and complex. https://www.sitepoint.com/xmlhttprequest-vs-the-fetch-api-whats-best-for-ajax-in-2019/. There is the first gotcha, though!
Điều này có thể làm cho bẫy lỗi phức tạp hơn để cài đặt. There are a lot of things to be remembered for XMLHttpRequest compared to the relatively simple Fetch API. To be able to view the content of this object the response is then converted using a .json() method.
Fetch returns a promise which prevents callback hell. Why do we need two .then()? Ví dụ phương thức jQuery.ajax(). Improving our debugging flow with Bisect and Worktree, Building forms with React Hook Form and TypeScript, React Context API with hooks and TypeScript, API with NestJS #13.
Avoiding Access-Control-Allow-Origin CORS error, 'https://jsonplaceholder.typicode.com/posts', API with NestJS #14. If you would like to know more about cookies, you might be interested in Cookies: explaining document.cookie and the Set-Cookie header. To do that, you need to set the credentials option. JSON Placeholder is an awesome service for testing API calls. Các interface về Headers, Request, Response được cung cấp một cách nhất quán, Promises cho phép xâu chuỗi một cách dễ dàng hơn và async/await không có callback. XMLHttpRequest. Promises are resolved using .then() and .catch() receives errors if the request fails. you use the open function. This .json() also returns a promise so another .then() is necessary. In other words, even if the server responds in with a non-ok status, the request is treated as completed, and therefore successful. Tagged templates, Next article Cross-Origin Resource Sharing. To do this. The first .then() resolves the promise into a response object. For a list of the possible functions, check out the MDN documentation. Cần có thêm code để bọc Fetch trong một Promise khác, ví dụ: hay có thể sử dụng Promise.race() để giải quyết khi fetch hay timeouts hoàn thành trước: Thật dễ dàng để kết thúc một request XHR với xhr.abort(). No worries, we can easily create a function that returns a promise when using XHR. Let’s make a request like that to better understand what is happening inside of … Thanks to the knowledge on how the XMLHttpRequest works, you can understand better what happens under the hood of libraries like axios. Both of them use XMLHttpRequest (XHR). You can check the ok boolean property to make sure that the request succeeded.
Fetch API được hỗ trợ tương đối, tuy nhiên nó không hoạt động trên hầu hết các phiên bản của Internet Explorer. When fetch with keepalive isn't available, you can consider using the navigator.sendBeacon() API, which can support these use cases while typically delivering a good UX. It turns out that using an API is not as hard as I thought! © 2020 If you set it to false, the send function does not return until the request finishes.
Fetch API là một thay thế hiện đại cho XMLHttpRequest. All you do is pass the link to the API or resource as an argument using the fetch() method. The XMLHttpRequest.prototype inherits from the EventTarget.prototype. If you are using, for example, the POST method and you want to send some data, you need to put it into the argument of the send function. Implementing refresh tokens using JWT, Marcin Wanago Blog - JavaScript, both frontend and backend, people used some tricks to create sites that fetch additional data, When async is just not enough. The first difference that you see is that Fetch API uses promises. Đoạn code Javascript sau đây biểu thị một request HTTP GET cơ bản đến http://domain/service sử dụng XMLHttpRequest. You can send cookies with the cross-origin call using the withCredentials flag, but you can’t exclude them for all types of requests (aside from using the non-standard mozAnon flag). For more information check the MDN documentation. Since the state of the request changes as it progresses, you add an event listener to track the “readystatechange” and return data accordingly. The generic Headers, Request, and Response interfaces provide consistency while Promises permit … We use it here to send stringified JSON, but it accepts quite a few types of data. The first thing to do is to create an instance of an XMLHttpRequest object. Even though people used some tricks to create sites that fetch additional data before XMLHttpRequest, the introduction of XHR was quite a milestone in the history of web development. For simpler Ajax calls, XMLHttpRequest is lower-level, more complicated, and you will require wrapper functions. This method does the opening and closing of request, state change tracking, etc for you in the background. As you can see, such requests are asynchronous by default. Với các cuộc gọi Ajax đơn giản, XMLHttpRequest là cấp thấp và phức tạp và bạn sẽ cần đến các hàm bao bọc. If you wish to append some headers to your request, call the setRequestHeader after executing the open function.
If you want to read about threads in JavaScript, look into When async is just not enough. Another useful event is the error. Fetch API là một thay thế hiện đại cho XMLHttpRequest. With the Response object, you can handle more than just JSON.
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