title: How can I correctly check if a string does NOT contain a specific word?
body: <p>I am currently trying to figure out how to solve the above named problem.
  Specifically I want to check if the string does <em>not</em> contain the word "stream" both in capital and lowercase letters.</p>
  
  <p>Here's my code so far:</p>
  
  <pre><code>if (((gewaesser_name1.includes("Stream") == "false") ||
  (gewaesser_name1.includes("stream") == "false")) &amp;&amp;
  ((gewaesser_name2.includes("Stream") == "false") ||
  (gewaesser_name2.includes("stream") == "false")))
  {var a= "..."}
  </code></pre>
  
  <p>The code does obviously not work as the results are not what I expect them to be.
  I also tried to use the <code>indexOf</code> method before using the following syntax variations:</p>
  
  <pre><code>gewaesser_name2.indexOf("stream") == -1
  gewaesser_name2.indexOf("stream") &lt; 0
  </code></pre>
  
  <p>None of these variations seem to work for me. Could anyone please give me a hint what's the problem here? I used the <code>indexOf</code> method before many times but always when I wanted to check if a string did contain a specific word, not the other way round.</p>