Haskell style JSON stringification.

stringify.js

const stringify = (json, indent = 0) => {
  if (json === null || typeof json !== 'object') return JSON.stringify(json);

  const indentation = `\n${' '.repeat(indent)}`;

  if (Array.isArray(json)) {
    const { length } = json;

    if (length === 0) return '[]';

    let result = `[ ${stringify(json[0], indent + 2)}`;

    for (let i = 1; i < length; i += 1) {
      result += `${indentation}, ${stringify(json[i], indent + 2)}`;
    }

    return `${result}${indentation}]`;
  }

  const toString = ([key, val]) => {
    const result = val !== null && typeof val === 'object'
      ? `${indentation}  ${stringify(val, indent + 2)}`
      : ` ${JSON.stringify(val)}`;
    return `${JSON.stringify(key)}:${result}`;
  };

  const entries = Object.entries(json);

  const { length } = entries;

  if (length === 0) return '{}';

  let result = `{ ${toString(entries[0])}`;

  for (let i = 1; i < length; i += 1) {
    result += `${indentation}, ${toString(entries[i])}`;
  }

  return `${result}${indentation}}`;
};