title: How to calculate in JavaScript angle between 3 points?
body: <p>I want to get angle between 3 points in JavaScript.  </p>
  
  <p>If I have points <code>A(x1,y1)</code>, <code>B(x2, y2)</code> and <code>C(x3, y3)</code>, I want to get angle that is formed with lines AB and BC. </p>
  
  <pre><code>let A = {x:x1, y:y1}, B = {x:x2, y:y2}, C = {x:x3, y:y3}
  </code></pre>