const arr = [{a:5},{d:6},{g:0},{b:3},{c:1}];
let max = null;
let result;

for (const currentObj of arr) {
  const currentValue = currentObj[Object.keys(currentObj)[0]];
  const currentKey = Object.keys(currentObj)[0];

  if (max < currentObj[currentKey] || max === null) {
    max = currentValue;
    result = currentKey;
  }
}
console.log(result);

button{
  border: 1px solid #ffffff;
  padding-left: 40px;
  padding-right: 40px;
  padding-top: 10px;
  padding-bottom: 10px;
  background: none;
  transform: skewX(-15deg);
}
span {
  transform: skewX(15deg);
  font-size: 18px;
  color: rgb(255, 255, 255);
  text-transform: uppercase;
  display:block;
}