JSFiddle - React, Tailwind, and code Playground

JavaScript

RangeCheck = function(range) {
   this.init(range);
};

RangeCheck.prototype = {
  constructor: RangeCheck,
  /**
   * The range map.
   */
  range: null,

  init: function (range) {
    this.range = range || {};
  },

  putRange: function(name, max) {
    this.range[name] = max;
  },

  check: function(number) {
    for (var key in this.range) {
      if (this.range.hasOwnProperty(key)) {
        if (number <= this.range[key]) {
          return key;
        }
      }
    }
    return key;
  }
};

var rangeCheck = new RangeCheck({ small : 25, medium : 80, large : 150 });
var message = "15: " + rangeCheck.check(15) + "\n"
    + "25: " + rangeCheck.check(25) + "\n"
    + "85: " + rangeCheck.check(85) + "\n"
    + "850: " + rangeCheck.check(850) + "\n";
alert(message);
rangeCheck.putRange("veryLarge", 300);
var message = "15: " + rangeCheck.check(15) + "\n"
    + "25: " + rangeCheck.check(25) + "\n"
    + "85: " + rangeCheck.check(85) + "\n"
    + "850: " + rangeCheck.check(850) + "\n";
alert(message);