Deferreds -- Lightning talk notes

• Deferreds are values that might not exist yet
• But callbacks are used for letting you know that values exist
• Deferreds are objects — they can be passed about
• Deferreds can be successful and fail — so we do not have to use sentinel values
• Deferreds’ callback/errback can be chained
• A failed callback/errback calls the next errback in the chain
• A successful callback/errback calls the next callback in the chain
• If you like being able to find your bugs finish your deferres with log.err
• Use defer.succeed/defer.fail to make sure you’re always retunring the same type
• Use maybeDeferred to make sure that your users are not paying for your infrastructure’s mistake

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