best-practices

Common jq Reduce Patterns: 9 Essential Techniques for JSON Aggregation

April 11, 2026 jqlang/jq ↗

The reduce operator iterates over JSON values while maintaining an accumulator state, enabling everything from simple sums to complex grouping operations through the syntax reduce source as $var (init; body).

The reduce operator is a foundational construct in the jqlang/jq JSON processor. Unlike simple mapping operations, reduce maintains state across iterations through an accumulator variable, making it essential for aggregation tasks. According to the jq source code, the operator is tokenized as REDUCE in

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