title: Showing undefined along with the string when iterating object
body: <p>When i tried to iterate object and i want to convert it into a string to append the URL, but undefined is showing along with the string?</p>
  
  <p>This is my function to convert object to string</p>
  
  <pre><code>onFormattedFilterChange(urlParams) {
      let formattedParams;
      Object.keys(urlParams).forEach((item, i) =&gt; {
        formattedParams += '&amp;' + item + '=' + urlParams[item];
      });
    }
  </code></pre>
  
  <p>Where my urlParams</p>
  
  <pre><code>{projectType: "FP", status: "COMPLETE", code: "SG", executionType: "INTERNAL"} 
  </code></pre>
  
  <p>I want  string in the form of</p>
  
  <pre><code>&amp;projectType=FP&amp;status=COMPLETE&amp;code=SG&amp;executionType=INTERNAL
  </code></pre>
  
  <p>But instead of this it is showing </p>
  
  <pre><code>undefined&amp;projectType=FP&amp;status=COMPLETE&amp;code=SG&amp;executionType=INTERNAL
  </code></pre>
  
  <p>Why it showing undefined?</p>