stringify.js

'use strict';

const isObject = o => o && Object.prototype.toString.call(o) === '[object Object]';

function indenter (indentation) {
  if (!(indentation > 0)) {
    return txt => txt;
  }
  var space = ' '.repeat(indentation);
  return txt => {

    if (typeof txt !== 'string') {
      return txt;
    }

    const arr = txt.split('\n');

    if (arr.length === 1) {
      return space + txt;
    }

    return arr
      .map(e => (e.trim() === '') ? e : space + e)
      .join('\n');
  };
}

const clean = txt => txt
  .split('\n')
  .filter(e => e.trim() !== '')
  .join('\n');

function stringify (a, indentation) {
  const cr = (indentation > 0) ? '\n' : '';
  const indent = indenter(indentation);

  function rec(a) {
    let body = '';
    let isFlat = true;

    let res;
    const isEmpty = a.some((e, i, arr) => {
      if (i === 0) {
        res = '<' + e;
        return (arr.length === 1);
      }

      if (i === 1) {
        if (isObject(e)) {
          Object.keys(e).map(key => {
            let val = e[key];
            if (Array.isArray(val)) {
              val = val.join(' ');
            }
            res += ' ' + key + '="' + val + '"';
          });
          if (arr.length === 2) {
            return true;
          }
          res += '>';
          return;
        }
        res += '>';
      }

      switch (typeof e) {
      case 'string':
      case 'number':
      case 'boolean':
      case 'undefined':
        body += e + cr;
        return;
      }

      isFlat = false;
      body += rec(e);
    });

    if (isEmpty) {
      return res + '/>' + cr; // short form
    }

    return isFlat
      ? res + clean(body) + '</' + a[0] + '>' + cr
      : res + cr + indent(body) + '</' + a[0] + '>' + cr;
  }

  return rec(a);
}

module.exports = stringify;