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Many libraries provide promise objects that can also be used with await, as long as they match the specification for native JavaScript promises. However, promises from the jQuery library were not Promises/A+ compatible until jQuery 3.0. [22] Here's an example (modified from this [23] article):
The terms future, promise, delay, and deferred are often used interchangeably, although some differences in usage between future and promise are treated below. Specifically, when usage is distinguished, a future is a read-only placeholder view of a variable, while a promise is a writable, single assignment container which sets the value of the ...
JavaScript Object Notation (JSON) is often used as an alternative format for data interchange, [15] although other formats such as preformatted HTML or plain text can also be used. [16] A variety of popular JavaScript libraries, including JQuery, include abstractions to assist in executing Ajax requests.
Google Chrome DevTools, Console tab The "triangle" can be clicked to reveal some hidden info.. Click on the "Console" tab; Scroll to the bottom of the console and look for log entries in yellow and red.
In event driven architectures, synchronous transactions can be achieved through using request-response paradigm and it can be implemented in two ways: [16] Creating two separate queues: one for requests and the other for replies. The event producer must wait until it receives the response. Creating one dedicated ephemeral queue for each request.
The response can be parsed from the JSON format into a readily usable JavaScript object, or processed gradually as it arrives rather than waiting for the entire text. [14] The request can be aborted prematurely [ 15 ] or set to fail if not completed in a specified amount of time.
They are commonly used to send message updates or continuous data streams to a browser client and designed to enhance native, cross-browser streaming through a JavaScript API called EventSource, through which a client requests a particular URL in order to receive an event stream.
An additional potential problem is that the select and the I/O operations are still sufficiently decoupled that select's result may effectively be a lie: if two processes are reading from a single file descriptor (arguably bad design) the select may indicate the availability of read data that has disappeared by the time that the read is issued ...