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FOR EACH Loops

FOR EACH iterates over array-like values and executes a block for every item.

Basic loop

FOR EACH item IN input.items {
    OUTPUT { name: item.name };
}

The loop reads input.items and outputs each element's name field.

Filtering items

An optional WHERE clause keeps only matching elements.

FOR EACH item IN input.items WHERE item.qty > 1 {
    OUTPUT { name: item.name, qty: item.qty };
}

Only items with quantity greater than 1 reach the body.

Mutating within a loop

Use SET to update accumulators as you iterate: 

LET totals = { count: 0, sum: 0 };

FOR EACH item IN input.items WHERE item.qty > 0 {
    SET totals.count = totals.count + 1;
    SET totals.sum = totals.sum + item.qty;
}

OUTPUT totals;

Tips

  • FOR is a synonym of FOR EACH.
  • WHERE is optional; omit it when you don’t need filtering.
  • Use LET inside the loop for per-item scratch variables; use SET to mutate values defined outside the loop.
  • For single-expression transformations, consider array comprehensions instead.

Try it

Load the collection-transforms example in the playground and compare the loop to MAP/FILTER/REDUCE alternatives.