title: Is there a simple way to loop through an object who's values are arrays of objects to generate a list from those object's values
body: <p>I have a JSON object I am importing into a react page that's similar to the following:</p>
  
  <pre><code>const obj1 = {
    "January": [
      {
        "Id": 1,
        "FileName": "some file",
        "Format": "Excel (.xlsx)",
        "Category": "some category 1",
        "Start": "01/01/2019",
        "End": "12/31/2019",
        "Created": "01/09/2019"
      },
      {
        "Id": 2,
        "FileName": "some big file",
        "Format": "Excel (.xlsx)",
        "Category": "some category 2",
        "Start": "01/01/2018",
        "End": "12/31/2018",
        "Created": "01/09/2019"
      }
    ],
    "February": [
      {
        "Id": 3,
        "FileName": "some small file",
        "Format": "PDF (.pdf)",
        "Category": "some category 3",
        "Start": "01/01/2018",
        "End": "12/31/2018",
        "Created": "01/09/2019"
      },
      {
        "Id": 4,
        "FileName": "some other file",
        "Format": "Excel (.xlsx)",
        "Category": "some category 4",
        "Start": "01/01/2018",
        "End": "12/31/2018",
        "Created": "01/09/2018"
      }
    ],
    "March": [
      {
        "Id": 55,
        "FileName": "some file again",
        "Format": "Excel (.xlsx)",
        "Category": "some category 5",
        "Start": "01/01/2017",
        "End": "12/31/2017",
        "Created": "01/09/2017"
      }
    ]
  };
  </code></pre>
  
  <p>and I want to loop through the above objects and dynamically populate a select dropdown element's options with each unique category. </p>
  
  <p>The select would look something like this: </p>
  
  <pre><code>&lt;select className="selectpicker" data-width="fit" value="All" onChange={this.addSomeOptions}&gt;
    &lt;option &gt;Category 1&lt;/option&gt;
    &lt;option &gt;Category 2&lt;/option&gt;
    &lt;option &gt;Category 3&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>Is there a good way to do this? Thanks!</p>