javascript - 尝试在对象上使用 .reduce

Question

所以我有一个对象，我需要为所有对象求和一个嵌套值。我的对象看起来像

const json = [
{
    "other_sum": "1",
    "summary": {
        "calculations": {
            "time": 10,
            "unit": 25
        },
        "updated": "2020-06-05"
    }
},
{
    "other_sum": "1",
    "summary": {
        "calculations": {
            "time": 20,
            "unit": 5
        },
        "updated": "2020-06-05"
    }
},
{
    "other_sum": "1",
    "summary": {
        "calculations": {
            "time": 5,
            "unit": 15
        },
        "updated": "2020-06-05"
    }
},
];

我需要总结所有“单位”值
我一直在尝试为此使用 .reduce ，但它仅在我的对象中有 2 个项目时才有效，一旦我得到第 3 个项目，我就会出错。
我的其余代码如下:

const r = json.reduce((a, b) => a.summary.calculations.unit + b.summary.calculations.unit);
console.log(r);

不太确定我在做什么错atm。

Answer 1

因为那不是方式reduce作品。取自 this article它是这样工作的:

Given

arrSum = function(arr){
  return arr.reduce(function(a,b){
    return a + b
  }, 0);
}

The function that we pass as the first parameter of the reduce methodreceives two parameters, a and b. In this code, a is our accumulator.It will accumulate our sum as our function works. b is the currentvalue being processed.

所以基本上你试图访问累加器中的“摘要”，这只是一个数字。这是工作片段:

json = [
{
    "other_sum": "1",
    "summary": {
        "calculations": {
            "time": 10,
            "unit": 25
        },
        "updated": "2020-06-05"
    }
},
{
    "other_sum": "1",
    "summary": {
        "calculations": {
            "time": 20,
            "unit": 5
        },
        "updated": "2020-06-05"
    }
},
{
    "other_sum": "1",
    "summary": {
        "calculations": {
            "time": 5,
            "unit": 15
        },
        "updated": "2020-06-05"
    }
},
];

const r = json.reduce((a, b) => a + b.summary.calculations.unit, 0);
console.log(r);