title: Addition of two strings gives unintended result
body: <p>I would like to get a numeric value in a string which is in the format <code>1 111</code>. </p>
  
  <p>I used a regex to extract it: 
  <code>([0-9]*)\s([0-9]*)</code></p>
  
  <p>then I thought that I will obtain the correct result with this operation: 
  <code>regex_result[1]*1000+regex_result[2]</code></p>
  
  <p>But actually I just have to addition them and I do not understand why. </p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>var str= "Bit rate                                 : 5 333 kb/s"
  
  var bitrate= str.match(/Bit\srate\s*:\s([0-9]*)\s([0-9]*)\s/);
  console.log(bitrate);
  
  //attempted result, but incorrect code
  console.log(bitrate[1]+bitrate[2]);
  
  //attempted correct code, but wrong result
  console.log(bitrate[1]*1000+bitrate[2]);</code></pre>
  </div>
  </div>
  </p>