如何使用 forEach 列出部分总和 [英] How to make a list of partial sums using forEach

问题描述

我有一个数组，看起来像这样:

I have an array of arrays which looks like this:

changes = [ [1, 1, 1, -1], [1, -1, -1], [1, 1] ];

我想通过添加最后一个值来获取数组中的下一个值

I want to get the next value in the array by adding the last value

values = [ [1, 2, 3, 2], [1, 0, -1], [1, 2] ];

到目前为止，我已经尝试使用 forEach:

so far I have tried to use a forEach:

changes.forEach(change => {
    let i = changes.indexOf(change);
    let newValue = change[i] + change[i + 1]
});

我认为我在正确的路线上，但我无法让这种方法发挥作用，或者可能有更好的方法来做到这一点.

I think I am on the right lines but I cannot get this approach to work, or maybe there is a better way to do it.

推荐答案

您可以保存总和并添加值.

You could save a sum and add the values.

var array = [[1, 1, 1, -1], [1, -1, -1], [1, 1]],
    result = array.map(a => a.map((s => v => s += v)(0)));

console.log(result);

通过使用forEach，您需要取对象引用和前一个值或零.

By using forEach, you need to take the object reference and the previous value or zero.

var array = [[1, 1, 1, -1], [1, -1, -1], [1, 1]];

array.forEach(a => a.forEach((v, i, a) => a[i] = (a[i - 1] || 0) + v));

console.log(array);

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