Confusion using parenthesis with and or
<p>I'm new to Javascript, but in my head the below statement should be false if I don't type 'yes' or 'no'. However, the script seems to be ignoring this, and just returning true or false depending on whether a=1 or not. Can someone exlain what I'm doing wrong? Many thanks in advance.</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>var a = 1;
var box1 = prompt("Type 'yes' or 'no' for statement to be true");
if ((box1 === "yes" || "no") &amp;&amp; a === 1) {
  alert("Hooray!");
} </code></pre>
</div>
</div>
</p>