title: Use strict and let not working as expected in Javascript
body: <p>I declared variables twice in my function while I am using "use strict". I know this function has global scope and it's variables are also treated as global with window scope i.e window.car</p>
  
  <p>But It should not re-declare speed and capacity variables inside if statement with let data type. ( "let" Declares a block scope local variable, optionally initializing it to a value. ) </p>
  
  <pre><code>(function car() {
      "use strict";
      var speed = 100;
      const capacity = '1000CC';
  
      if(speed)  {
          let speed = 200;
          let capacity = '5000CC';
          console.log(speed,capacity);
  
      }
      console.log(speed,capacity);
  
  })();
  </code></pre>
  
  <p>Please let me know what I am missing here.</p>