Type Alias JoinCSVFields<Chars, Delimiter, Quotation, Nl>

JoinCSVFields: Chars extends readonly [infer F, ...(infer R)]
    ? F extends string
        ? R extends string[]
            ? `${F extends `${string}${Nl
            | Delimiter
            | Quotation}${string}`
                ? `${Quotation}${F}${Quotation}`
                : F}${R extends [] ? "" : Delimiter}${JoinCSVFields<
                R,
                Delimiter,
                Quotation,
            >}`
            : string
        : string
    : ""

Join CSV field array into a CSV-formatted string with proper escaping.

Type Parameters

Chars extends ReadonlyArray<string | number | boolean | bigint>
Delimiter extends string = DEFAULT_DELIMITER
Quotation extends string = DEFAULT_QUOTATION
Nl extends string = Exclude<Newline, Delimiter | Quotation>

Remarks

This type handles CSV-specific formatting:

Quotes fields containing delimiters, quotations, or newlines
Joins fields with the specified delimiter

Example: Default

const header = ["name", "age", "city", "zip"];

type _ = JoinCSVFields<typeof header>
// `name,age,city,zip`

Example: With different delimiter and quotation

const header = ["name", "a\nge", "city", "zip"];

type _ = JoinCSVFields<typeof header, "@", "$">
// `name@$a\nge$@city@zip`