How to format XML string in JavaScript

test.js

  function formatXML(xml, tab = '  ', nl = '\n') {
    let formatted = '', indent = '';
    const nodes = xml.slice(1, -1).split(/>\s*</);
    if (nodes[0][0] == '?') formatted += '<' + nodes.shift() + '>' + nl;
    for (let i = 0; i < nodes.length; i++) {
      const node = nodes[i];
      if (node[0] == '/') indent = indent.slice(tab.length); // decrease indent
      formatted += indent + '<' + node + '>' + nl;
      if (node[0] != '/' && node[node.length - 1] != '/' && node.indexOf('</') == -1) indent += tab; // increase indent
    }
    return formatted;
  }