JSFiddle - React, Tailwind, and code Playground

HTML

<input type="number"
  id="grade"
  value=""
  min="0" max="100">
<input type="button" value="Grade" onclick="RateScores()">

JavaScript

function RateScores() {    
    var score = document.getElementById("grade").value;
    var result = "";
    var step = Math.floor(score/10);
    switch (step) {
        case 6: 
            result = "You got a D";
            break;
        case 7: 
            result = "You got a C";
            break;
        case 8: 
            result = "You got a B";
            break;
        case 9: 
            result = "You got a A";
            break;
        case 10: 
            result = "Perfect score!";
            break;
        default: 
            result = "Failure.";
            break;
    }
    alert(result);
}