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Learning Path

Promise Mistakes

Fix the promise patterns that cause undefined values, swallowed errors, and batch failures.

Step 1

Missing return

Keep values flowing through .then chains.

Step 2

Error in then

See how thrown errors become promise rejections.

Step 3

Promise.all fail

Know when one failure cancels the group.

Step 4

Promise.all vs allSettled

Choose fail-fast or partial success intentionally.