title: Strange behaviour of array.includes returning always false for string 'sku'
body: <p>I'm facing strange behaviour of array.includes functionality.
  My job is to check if variable feedProduct has all required fields.</p>
  <pre><code>function hasAllRequiredFields(requiredFields, feedProduct) {
      
      // Prepare array for adding missing fields
      let missing_required = [];
      
      // Print all fields and there type (only for easier debugging)
      console.log(feedProduct);
      console.log(typeof feedProduct);
      feedProduct.forEach(fp =&gt; {
          console.log(fp)
          console.log(typeof fp)
      })
      
      // Check if feedProduct array contains all required fields
      console.log('')
      console.log('CHECK IF ALL REQUIRED FIELDS ARE PRESENT')
      requiredFields.forEach(wf =&gt; {
          console.log(wf);
          console.log(typeof wf);
          if (!feedProduct.includes(wf)) {
              missing_required.push(wf);
          }
      })
      
      console.log('')
      console.log('')
      console.log('Missing')
      console.log(missing_required)
      
      return missing_required;
  }
  </code></pre>
  <p>And the result is so strange. As you can see i'm searching for string 'sku' type of string in array FeedProduct, which includes string 'sku' of type of String, but <code>feedProduct.includes(wf)</code> returns false</p>
  <p><a href="https://i.stack.imgur.com/Pk8vx.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Pk8vx.jpg" alt="sku missing" /></a></p>
  <p>I've also tried the same logic with indexOf and result is the same. If I copy/paste this code in Developer tools, then result will be true and no fields will be missing</p>
  <p>Can some please point me what else should I check or do, so my code will be working properly. If you need any additional informations, please let me know and I will provide. Thank you</p>
  <p>**UPDATE</p>
  <p>function is called in some other function, like this</p>
  <pre><code>let hasRequiredFields = hasAllRequiredFields(preparedMappingFields.storeFeedMustHaveFields, header);
  </code></pre>
  <p>result for <code>console.log(feedProduct[0], requiredFields[0], feedProduct[0] === requiredFields[0]);</code> is following</p>
  <p>sku sku false</p>
  <p>** UPDATE TWO</p>
  <pre><code>console.log(requiredFields[0].split('').map(c =&gt; c.charCodeAt(0)))
  console.log(feedProduct[0].split('').map(c =&gt; c.charCodeAt(0)))
  
  Log 1:
  [ 115, 107, 117 ]
  Log 2:
  [ 65279, 115, 107, 117 ]
  </code></pre>