Javascript:循环只打印最后一个值

var arr = [1, 2, 3, 4, 5];
var lastValue;

for (var i = 0; i < arr.length; i++) {
  lastValue = arr[i];
}

console.log(lastValue);

var arr = [1, 2, 3, 4, 5];
var lastValue;

arr.forEach(function(element, index, array) {
  if (index === array.length - 1) {
    lastValue = element;
  }
});

console.log(lastValue);

var arr = [1, 2, 3, 4, 5];

var lastValue = arr.reduce(function(accumulator, currentValue, currentIndex, array) {
  if (currentIndex === array.length - 1) {
    return currentValue;
  } else {
    return accumulator;
  }
});

console.log(lastValue);