title: How to concatenate string and numbers to make a JSON object?
body: <p>I want to make a JSON object like this:</p>
  
  <pre><code>let lob =  { courses_dept: 'sci', courses_avg: 77.09 };
  </code></pre>
  
  <p>by concatenate variables together:</p>
  
  <pre><code>var dept = "sci";
  var avg = 77.09;
  
  let a = '{"courses_dept": dept, "courses_averge": avg }';
  </code></pre>
  
  <p>but I got SyntaxError if I do this:</p>
  
  <pre><code>let b = JSON.parse(a); 
  </code></pre>
  
  <p>What is the proper way to do this?</p>