$in
Reference group: Conditional and logical expressions
What it does
Aggregation $in checks whether a value is in an array.
Syntax
{$in: [value, array]}
Use case
Evaluate membership in computed lists.
Important notes
Different syntax from query predicate $in.
$in: practical example
{ $project: { allowed: { $in: ["$role", ["admin", "editor"]] } } }💡 Explanation
Aggregation
$in checks whether a value is in an array.
When to use it
Evaluate membership in computed lists.
Caution
Different syntax from query predicate $in.Key Takeaways
- Aggregation
$inchecks whether a value is in an array. - Typical use: Evaluate membership in computed lists.