JSFiddle - React, Tailwind, and code Playground

JavaScript

let netprofitper = 0.45;

const list = {
  0: "E1",
  0.11: "D2",
  0.21: "D1",
  0.31: "C2",
  0.41: "C1",
  0.51: "B2",
  0.61: "B1",
  0.71: "A2",
  0.81: "A1",
  0.91: "A++",
};

let previous = 0;

Object.keys(list).some(k => {
  if (k > netprofitper) {
    return true;
  } 
  previous = k
});

var code = list[previous];
alert(code);