All files / dotenv / stringify.ts

// Copyright 2018-2026 the Deno authors. MIT license.
// This module is browser compatible.

/**
 * Stringify an object into a valid `.env` file format.
 *
 * @example Usage
 * ```ts
 * import { stringify } from "@std/dotenv/stringify";
 * import { assertEquals } from "@std/assert";
 *
 * const object = { GREETING: "hello world" };
 * assertEquals(stringify(object), "GREETING='hello world'");
 * ```
 *
 * @param object object to be stringified
 * @returns string of object
 */
export function stringify(object: Record<string, string>): string {
  const lines: string[] = [];
  for (const [key, value] of Object.entries(object)) {
    let quote;

    let escapedValue = value ?? "";
    if (key.startsWith("#")) {
      // deno-lint-ignore no-console
      console.warn(
        `key starts with a '#' indicates a comment and is ignored: '${key}'`,
      );
      continue;
    } else if (
      escapedValue.includes("\n") ||
      escapedValue.includes("\r") ||
      escapedValue.includes("\t") ||
      escapedValue.includes("'") ||
      escapedValue.includes("\\")
    ) {
      // Escape backslashes first so we don't double-escape sequences we add
      // below (e.g. so a literal `\n` (backslash-n) is preserved distinctly
      // from a real newline).
      escapedValue = escapedValue
        .replaceAll("\\", "\\\\")
        .replaceAll("\n", "\\n")
        .replaceAll("\r", "\\r")
        .replaceAll("\t", "\\t");
      quote = `"`;
    } else if (escapedValue.match(/\W/)) {
      quote = "'";
    }

    if (quote) {
      // escape inner quotes
      escapedValue = escapedValue.replaceAll(quote, `\\${quote}`);
      escapedValue = `${quote}${escapedValue}${quote}`;
    }
    const line = `${key}=${escapedValue}`;
    lines.push(line);
  }
  return lines.join("\n");
}