JavaScript push()问题

Question

你能告诉我，为什么最终的数组没有初始数组的最后一项；，它返回[3, 6, 9, 2, 4, 6]，而我们缺少'8'。

let item = [123,456,789,12,34,56,78];
const tailAndHead = arr => arr.slice(1).reduce((a,v,i) => (a.push(arr[i]%10), a),  []);

Answer 1

为什么不使用Array#map

tailAndHead = arr.map(a => a % 10);

Answer 2

移除切片(1)。

let item = [123,456,789,12,34,56,78];

const tailAndHead = arr => arr.reduce((a,v,i) => (a.push(arr[i]%10), a),  []);

Answer 3

您应该推送切片数组项。请像这样修改你的代码。

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let item = [123,456,789,12,34,56,78];
const tailAndHead = arr => arr.slice(1).reduce((a,v,i,b) => (a.push(b[i]%10), a),  []);
console.log(tailAndHead(item));

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