程序代写 ASYNCHRONOUS PROGRAMMING – cscodehelp代写

ASYNCHRONOUS PROGRAMMING
Andrew College Boston University

WHAT IS A PROMISE?

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A Promise is a proxy for a value not
necessarily known when the promise is created.
A promise represents WORK that needs to be done at some point.

You can use it everywhere but not with Internet Explorer.
EVERYWHERE

Synchronous
One expression at a time.
Asynchronous
The next expression runs while the previous finishes up.
DIFFERENCES

STANDARD EXAMPLE

THEN() – CAN BE USED MULTIPLE TIMES

Every use of .then() will
that you can use again.
CHAINING PROMISES

PROMISE.ALL()

PROMISE.ALL()
The all() method takes an iterable of promises as input, and returns a single Promise that resolves to an array of the results of the input promises, in order.

RACE() – WAIT UNTIL ANY PROMISE WORKS OR FAILS

CATCHING ERRORS
The catch() returns a Promise.
Deals w/rejected cases only.

CATCH() IS JUST A FORM OF THEN()
The catch() is just like then() without a callback function for success.

METHODS YOU NEED TO UNDERSTAND

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