mdn/js/3_async_javascript/1_how_to_use_promises

1_how_to_use_promises

dz / mdn / js / 3_async_javascript / 1_how_to_use_promises

Summary

How to use promises

Node Tree

Nodes

promises
content promises
children catching_errors, chaining_promises, fetch_API, foundation_async_programming, handlers_attach_promise, obj_ret_async_cur_state (description)

foundation_async_programming
content foundation of asynchronous programming in JavaScript
parents promises

obj_ret_async_cur_state
content Object returned by an asynchronous function which represents the current state of operation
parents promises

handlers_attach_promise
content handlers attached to promise object are executed when oepration succeeds/fails
parents promises

fetch_API
content fetch() API
children promise_replacement_XMLHttpRequest (description)
parents promises

promise_replacement_XMLHttpRequest
content promise-based replacement for XMLHttpRequest
parents fetch_API

chaining_promises
content Chaining Promises
children promise_chaining, then_returns_promise
parents promises

promise_chaining
content Promise Chaining: return promise, call then() on it.
parents chaining_promises

then_returns_promise
content then() itself returns a promise, which will be completed with the result of the function passed to it.
parents chaining_promises

catching_errors
content catching errors
children catch_method
parents promises

catch_method
content catch() method
children called_on_any_failure_when_at_end
parents catching_errors

called_on_any_failure_when_at_end
content when placed at end of chain, will be called when any of the asynchronous functions fail
parents catch_method

promise_terminology
content Promise terminology
children rejected, settled, fulfilled, pending

pending
content pending: promise created, async function created with it has yet to succeed or fail
parents promise_terminology

fulfilled
content Fulfilled: async function suceeded, then() handler called
parents promise_terminology

rejected
content Rejected: async func failed. Catch() handler called.
parents promise_terminology

combining_multiple_promises
content Combining mUltiple promises
children promise_all

promise_all
content promise.all(): takes array of promises and returns single promise
children promise_all_fulfilled_rejected, promise_any (fulfilled when any promise in array fulfilled)
parents combining_multiple_promises

settled
content Settled: covers both fulfilled and rejected
parents promise_terminology

promise_all_fulfilled_rejected
content fulfilled when and if all promises fulfilled. rejected when and if any are rejected.
parents promise_all

promise_any
content promise.any(): like promise.all(), but fulfilled when any promises in array are fulfilled
parents promise_all

async_await
content Async and Await
children async, await

await
content await: used inside async function before function call that returns promise.
children similar_to_promise_chain, make_async_look_sync (description), only_used_async_or_module
parents async_await

async
content async: keyword before function declaration to make it asynchronous.
parents async_await

make_async_look_sync
content Enables code using async functions to look like synchronous code
parents await

only_used_async_or_module
content Only used in async function, unless code is inside a JS module
parents await

similar_to_promise_chain
content similar to promise chain, await forces async operations to be completed in series
parents await