.ref.boost__json__string.find_first_of.return_value">Return
          Value</a>
        </h6>
<p>
          The first occurrence of any of the characters within <code class="computeroutput"><span class="identifier">sv</span></code>
          within the string starting at the index <code class="computeroutput"><span class="identifier">pos</span></code>,
          or <a class="link" href="npos.html" title="string::npos"><code class="computeroutput"><span class="identifier">npos</span></code></a>
          if 