<script type="application/javascript;version=1.7">
      // let Statement
      var test = 10;
      let( test = 20 ) {
          alert( test ); // alerts out 20
      }
      alert( test ); // alerts 10
  
      // let Expression
      var test = 10;
      alert( let( test = 20 ) test ); // alerts out 20
      alert( test ); // alerts 10
  
      // let Definition
      var test = 10;
      if ( test == 10 ) {
          let newTest = 20;
          test += newTest;
      }
      alert( test ); // alerts 30
      alert( newTest ); // fails, newText is undefined outside of the if statement
  
      // Using let in a for block
      for ( let i = 0; i < 10; i++ ) {
          alert( i );
      }
      alert( i ); // fails, i is undefined outside of the for statement
  </script>