web-csv-toolbox - v0.15.0
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    ColumnCountStrategy Guide

    columnCountStrategy controls how the parser handles rows whose column counts differ from the header. The available strategies depend on the output format and whether a header is known in advance.

    Strategy Short rows Long rows Object Array (explicit header) Array (header inferred) Headerless (header: [])
    fill Pad with "" Trim excess columns ✅ ✅ ✅ ❌
    strict Throw error Throw error ✅ ✅ ✅ ❌
    keep Keep as-is (ragged rows) Keep as-is ❌ ✅ ✅ ✅ (mandatory)
    truncate Keep as-is Trim to header length ❌ ✅ ❌ (requires header) ❌
    sparse Pad with undefined Trim excess columns ❌ ✅ ❌ (requires header) ❌
    • Guarantees fixed-length records matching the header.
    • Object: missing values become "", enabling consistent string-based models.
    • Array output: missing values also become empty strings.

    strict

    • Treats any column-count mismatch as a fatal error, useful for schema validation.
    • Requires a header (explicit or inferred).

    keep

    • Leaves each row untouched. Arrays can vary in length, making it ideal for ragged data or headerless CSVs.
    • Headerless mode (header: []) enforces keep.

    truncate

    • Drops trailing columns that exceed the header length while leaving short rows untouched.
    • Only available when a header is provided (array output).

    sparse

    • Similar to fill, but pads missing entries with undefined. This is useful when you want to distinguish between missing and empty values.
    • Requires an explicit header to determine the target length.
    1. Need strict schema enforcement? Use strict.
    2. Need consistent string values? Use fill (object default).
    3. Need ragged rows / headerless CSV? Use keep (array output).
    4. Need to ignore trailing columns? Use truncate (array output with header).
    5. Need optional columns? Use sparse (array output with header).

    Pair this guide with the Output Format Guide to decide which combination best fits your workload.

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    ColumnCountStrategy Guide