Capstone: streaming CSV parser

Putting C6 together

A streaming CSV parser is the perfect generator capstone — it walks a string line by line, yielding one parsed row at a time. No need to materialize the whole table in memory.

The shape:

function* parseCsv(text) {
  const lines = text.trim().split("\n");
  const headers = lines[0].split(",");
  for (let i = 1; i < lines.length; i++) {
    const values = lines[i].split(",");
    const row = {};
    for (let j = 0; j < headers.length; j++) {
      row[headers[j]] = values[j];
    }
    yield row;
  }
}

You consume it with for-of. The capstone task takes a hard-coded CSV string, parses it, and sums a numeric column.

Why this matters

• The same generator shape works on ReadableStream chunks from fetch — turns a 100MB CSV download into a row-by-row stream.
• Async generators handle the streaming version (real fetch + TextDecoderStream).
• You only need C6-04 + C6-09 to do it. Generators are not theoretical.