unindent-template-array.ts

unindent-template.ts

const INDENTATION_RE = /^\n( +)/;

const unindentTemplate = (
  template: TemplateStringsArray,
): { readonly raw: readonly string[] } => {
  const indentation = INDENTATION_RE.exec(template.raw[0])?.[1];
  return indentation
    ? { raw: template.raw.map((a) => a.replaceAll(`\n${indentation}`, "\n")) }
    : template;
};

// example usage in another template function for markdown

const escapeMarkdown = (markdown: string) => markdown.replace(/(`)/g, "\\$1");
export type Markdown = { readonly MARKDOWN: string };

/** escape text substitutions for Markdown */
export const md = (
  template: TemplateStringsArray,
  ...substitutions: (Markdown | number | string | Record<string, unknown>)[]
) => {
  const subs = substitutions.map((a) =>
    typeof a === "object" && "MARKDOWN" in a
      ? a.MARKDOWN
      : escapeMarkdown(devStringify(a)),
  );

  return { MARKDOWN: String.raw(unindentTemplate(template), ...subs) };
};

// usage
function something() {
  // has trailing new line
  const ex1 = md`
    # Hello world
     - Good day
    `
  
  // no trailing new line
  const ex2 = md`
    # Hello world
     - Good day`
  
  // no indentation changes (same as ex1)
  const ex3 = md`# Hello world
- Good day
`
}