如何在 Array.reduce() 的回调函数中使用 Array.concat() 方法减少或展平数组数组

Question


//Bonus - uncomment lines 15 and 17
const arrays = [["how", "now"], ["brown", "cow"]];
const flattenedArray = arrays.reduce((a,c) => a + c);
// The below line should console.log: ["how", "now", "brown", "cow"]
console.log(flattenedArray);

我刚开始使用 reduce 函数，有点复杂。

我正在尝试展平嵌套数组，但我真的不知道下一步该怎么做。

Answer 1

您已经提到了解决方案，您只需要实施它 - concat 当前项目到 reduce 回调中的累加器：

const arrays = [["how", "now"], ["brown", "cow"]];
const flattenedArray = arrays.reduce((a,c) => a.concat(c));
console.log(flattenedArray);

但是 .flat() 会容易得多：

const arrays = [["how", "now"], ["brown", "cow"]];
const flattenedArray = arrays.flat();
console.log(flattenedArray);

Answer 2

另一种选择 - flatMap：

const arrays = [["how", "now"], ["brown", "cow"]];
const flattenedArray = arrays.flatMap(a => a);
console.log(flattenedArray);

但只有当你想在地图内部做一些事情时，它才真正有利，就像这样：

const arrays = [["how", "now"], ["brown", "cow"]];
const flattenedArray = arrays.flatMap(a => a.concat(a));
console.log(flattenedArray);

或者像这样：

const arrays = [["how", "now"], ["brown", "cow"]];
const flattenedArray = arrays.flatMap(a => a.map(b => b.toUpperCase()));
console.log(flattenedArray);

如何在 Array.reduce() 的回调函数中使用 Array.concat() 方法减少或展平数组数组

How can I reduce or flatten an array of arrays using the Array.concat() method inside the callback function for Array.reduce()

javascript

arrays

reduce

concatenation