if else java script

<script>
let result = prompt("enter the any number")
if(result >= 90 && result <=100){

    console.log("a garde");
} else   {
    if(result >= 70 && result <=89){

        console.log("b garde");
    } else{
        if(result >=60 && result <=69){
            console.log("c grade");
        } else {

    if(result >=50 && result <=59){

        console.log("d garde");
    }else {

        if(result >=0 && result<=49){

            console.log("f garde");
        }
    }
        }

    }


}
    </script>