Promise - JavaScript | MDN
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015. * Some parts of this feature may have varying levels of support. Learn more See full compatibility Report feedback The Promise object represents the eventual completion (or failure) of an asynchronous operation and its resulting value. To learn about the way pro
Promises/A+
Promises/A+ An open standard for sound, interoperable JavaScript promises—by implementers, for implementers. A promise represents the eventual result of an asynchronous operation. The primary way of interacting with a promise is through its then method, which registers callbacks to receive either a promise’s eventual value or the reason why the promise cannot be fulfilled. This specification detai
Promises
Motivation Consider the following synchronous JavaScript function to read a file and parse it as JSON. It is simple and easy to read, but you wouldn't want to use it in most applications as it is blocking. This means that while you are reading the file from disk (a slow operation) nothing else can happen. function readJSONSync(filename) { return JSON.parse(fs.readFileSync(filename, 'utf8')); } To
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JavaScript Promiseの本
