正如所料， d3.max （）确实返回了最大值...但是，它返回字符串中的最大值，而不是数字中的最大值。

As expected, d3.max() is indeed returning the maximum value... however, it is returning the maximum value among strings, not among numbers.

解释是，默认情况下， d3.csv（）会将所有值加载为字符串，即使它们是数字。因此，当你这样做时：

The explanation is that, by default, d3.csv() will load all the values as strings, even if they are numbers. Therefore, when you do:

var value = record[year];

value 是一个字符串，而不是一个数字。在JavaScript中，字符串数组的最大值与数组数组的最大值不同。例如，使用数字：

value is a string, not a number. And in JavaScript the maximum for an array of strings is different from the maximum for an array of numbers. For instance, using numbers:

var myArray = [1, 65, 9, 32, 42];
console.log(d3.max(myArray));

<script src="https://d3js.org/d3.v4.min.js"></script>

这是预期值。但是看看如果我们使用字符串会发生什么：

That's the expected value. But look what happens if we use strings:

var myArray = ["1", "65", "9", "32", "42"];
console.log(d3.max(myArray));

<script src="https://d3js.org/d3.v4.min.js"></script>

解决方案：将您的值更改为数字：

Solution: change your values to numbers:

var value = +record[year];