title: Use array.reduce to join strings with comma, but avoid the extra comma
body: <p>I have an array of objects to be transformed and merged into a single string with <code>array.reduce</code>.</p>
  
  <pre class="lang-js prettyprint-override"><code>const arr = [{id: 7, task: "foo"}, {id: 22, task: "bar"}]
  </code></pre>
  
  <p>The result should be <code>7. foo, 22. bar</code></p>
  
  <p>If I write this code, it will work but produce <code>, 7. foo, 22.bar</code>:</p>
  
  <pre class="lang-js prettyprint-override"><code>arr.reduce((pre,cur)=&gt; pre + `, ${cur.id}. ${cur.task}`, '')
  </code></pre>
  
  <p>How can I properly do this without the extra comma, preferably only in FP?</p>