title: How can I parse String to Int in an Angular expression?
body: <p>A number string '5'</p>
  
  <pre><code>var num_str = '5';
  </code></pre>
  
  <p>How can I parseInt and let below answers correct at the same time?</p>
  
  <pre><code>{{num_str + 1}}  // 6
  {{num_str - 1}}  // 4
  </code></pre>
  
  <p>parseInt can't be used in an Angular expression,</p>
  
  <pre><code>{{parseInt(num_str) - 1}}    
  </code></pre>
  
  <p>number filter can't do add and minus,</p>
  
  <pre><code>{{num_str - 1 | number}}
  </code></pre>
  
  <p>If anyone have useful suggestion, I will very appreciate of you</p>