d then concatenates the strings, with the
<code>separator</code> string interleaved between the elements.</p>
    </section>
    
    <section class="summary source-code" id="source">
      <h2><span>Implementation</span></h2>
      <pre class="language-dart"><code class="language-dart">String join([String separator = &quot;&quot;]) {
  int length = this.length;
  if (!separator.isEmpty) {
    if (length == 0) return &quot;&quot;;
    String first = &quot;${elementAt(0)}&quot;;
    if (length != this.length