Select option tag to string javascript

How to i change the value of this to a string

 <select name="blog[body]">
  <option value="volvo">hot</option>
  <option value="saab">bad</option>
  <option value="opel">good</option>
  <option value="audi">cool</option>
 </select>

so i can store it in my mongodb database. Right now it comes as undefined

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