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Async JavaScript by Trevor Burnham

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A Very Brief History of Promises

Promises have existed in many forms in many languages. The term was first used by C++ engineers on the Xanadu project, a forerunner to the Web. Promises were later used in the E programming language, which inspired Python developers to implement them in the form of the Twisted framework’s Deferreds.

Promises hit the JavaScript mainstream in 2007 when the Dojo framework, taking a cue from Twisted, added an object called dojo.Deferred. At the time, the relatively mature Dojo rivaled the fledgling jQuery framework in popularity. In 2009, citing dojo.Deferred as an influence, Kris Zyp proposed the CommonJS Promises/A spec.[31] That same year, Node.js made its first appearance. Node’s early iterations used Promises ...

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