如何在javascript中找到嵌套数组的最大值/最小值? [英] How to find the max/min of a nested array in javascript?

问题描述

我想找到嵌套数组的最大值，如下所示:

I want to find the maximum of a nested array, something like this:

a = [[1,2],[20,3]]
d3.max(d3.max(a)) // 20

但我的数组包含一个我想丢弃的文本字段:

but my array contains a text field that I want to discard:

a = [["yz",1,2],["xy",20,3]]
d3.max(a) // 20

推荐答案

如果你有一个嵌套的数字数组 (arrays = [[1, 2], [20, 3]]),嵌套 d3.max:

If you have a nested array of numbers (arrays = [[1, 2], [20, 3]]), nest d3.max:

var max = d3.max(arrays, function(array) {
  return d3.max(array);
});

或者等效地，使用 array.map:

var max = d3.max(arrays.map(function(array) {
  return d3.max(array);
}));

如果你想忽略字符串值，你可以使用 array.filter忽略字符串:

If you want to ignore string values, you can use array.filter to ignore strings:

var max = d3.max(arrays, function(array) {
  return d3.max(array.filter(function(value) {
    return typeof value === "number";
  }));
});

或者，如果您知道字符串总是在第一个位置，您可以使用 array.slice 效率更高一点:

Alternatively, if you know the string is always in the first position, you could use array.slice which is a bit more efficient:

var max = d3.max(arrays, function(array) {
  return d3.max(array.slice(1));
});

另一种选择是使用访问器函数，该函数为不是数字的值返回 NaN.这将导致 d3.max 忽略这些值.方便的是，JavaScript 的内置 Number 函数正是这样做的，所以你可以说:

Yet another option is to use an accessor function which returns NaN for values that are not numbers. This will cause d3.max to ignore those values. Conveniently, JavaScript's built-in Number function does exactly this, so you can say:

var max = d3.max(arrays, function(array) {
  return d3.max(array, Number);
});

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