JSFiddle - React, Tailwind, and code Playground

JavaScript

var validCoins = {
      "nickel": {
        "weight": 5.00,
        "diameter": 21.21,
        "thickness": 1.95,
        "value": 0.05
      },
      "dime": {
        "weight": 2.27,
        "diameter": 17.91,
        "thickness": 1.35,
        "value": 0.10
      },
      "quarter": {
        "weight": 5.67,
        "diameter": 24.26,
        "thickness": 1.75,
        "value": 0.25
      }
    };
    
for (var key in validCoins) {
  if (validCoins.hasOwnProperty(key)) {
    alert(validCoins[key].weight);
  }
}