open_in_new content_copy 
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body{
            background-color: antiquewhite;
            color: black;
            text-align: center;
        }
    </style>
</head>
<body>
    <script>
                console.log("K before declaring=",k);
                var k;  
               function vardemo()
                 { 
                    {
                    var k=7;
                    console.log("K after decalring in function=",k);
                    var k=77;
                 }
                      console.log("K value after assigning value in same block",k);
                      }
                      vardemo();
            console.log("k after funtion=",k);           
            var k=8;
            console.log("K after assigning value =",k);    
            
            
            let a;
            console.log("a before intlization=",a);
            a=15;
            console.log("after declaration a=",a)
            function f()
            {
                let a=10;
                if(true)
                {
                    let a=20;
                    console.log("a after declaring in function=",a);
                }
                console.log("after block a=",a);
            }
            f();
            a=16;
            console.log("after declaring again a=",a);

            try {
                    const n=90;
                    console.log(" constant n=",n);
                    n=89;
                    console.log(" constant number after assigning again=",n);
                    
            }catch(e){ 
                       {console.log("Error :",e.message);}

                    } 
                   
    </script>
    
</body>
</html>