array.reduce和空值

我正在開發一個基于 javascript 的應用程式，其中我有一個陣列，如下所示：

[-12.66, 268.2, 48.99, -1264.5, 20550, 91.2, 0, 0, 0, 0, 0, 0, 0, 0, 9235.5, 1500, 0, 0, 18.99, 0, 0, null, null, null, null, null, null, null, null, null, null]

現在我想對以下錯誤進行累積求和，直到它回傳空值，一旦它開始讀取空值，它應該從那里回傳 null 或者應該按原樣回傳并且不應該從那里進行累積求和。

我已經使用以下方法完成了array.reduce：

let resultArray=[];
array1.reduce(function (acc, curr, index) {  return resuleArray[index] = acc   curr }, 0); 
// here array1 is source array.

但是，這將回傳如下

[-12.66, 255.54, 304.53, -959.97, 19590.03, 19681.23, 19681.23, 19681.23, 19681.23, 19681.23, 19681.23, 19681.23, 19681.23, 19681.23, 28916.73, 30416.73, 30416.73, 30416.73, 30435.72, 30435.72, 30435.72, 30435.72, 30435.72, 30435.72, 30435.72, 30435.72, 30435.72, 30435.72, 30435.72, 30435.72, 30435.72];

我想要的如下：

[-12.66, 255.54, 304.53, -959.97, 19590.03, 19681.23, 19681.23, 19681.23, 19681.23, 19681.23, 19681.23, 19681.23, 19681.23, 19681.23, 28916.73, 30416.73, 30416.73, 30416.73, 30435.72, 30435.72, null, null, null, null, null, null, null, null, null, null, null];

請注意，我將始終將尾隨值設為空。

uj5u.com熱心網友回復：

所以，檢查是否curr是null.

const array1 = [-12.66, 268.2, 48.99, -1264.5, 20550, 91.2, 0, 0, 0, 0, 0, 0, 0, 0, 9235.5, 1500, 0, 0, 18.99, 0, 0, null, null, null, null, null, null, null, null, null, null];

let resultArray = [];
array1.reduce(function(acc, curr, index) {
  const sum = acc   curr;
  if (curr === null) {
    resultArray[index] = null;
  } else {
    resultArray[index] = sum
  }
  return sum;
}, 0);

console.log(resultArray);

這樣，即使您在某些null值之后放置一個數字，它也會繼續累積總和

uj5u.com熱心網友回復：

你只需要像這樣修改一點你的代碼：

array1.reduce(function (acc, curr, index) {  
  return resultArray[index] = curr !== null ? acc   curr : null 
}, 0);

uj5u.com熱心網友回復：

您可以關閉總和并添加直到值 is null。

const
    data = [-12.66, 268.2, 48.99, -1264.5, 20550, 91.2, 0, 0, 0, 0, 0, 0, 0, 0, 9235.5, 1500, 0, 0, 18.99, 0, 0, null, null, null, null, null, null, null, null, null, null],
    result = data.map((sum => v => v === null ? null : sum  = v)(0));

console.log(...result);

uj5u.com熱心網友回復：

解釋 null 后在索引的其余部分插入 null

const array1 = [-12.66, 268.2, 48.99, -1264.5, 20550, 91.2, 0, 0, 0, 0, 0, 0, 0, 0, 9235.5, 1500, 0, 0, 18.99, 0, 0, null, null, null, null, null, null, null, null, null, null];
let resultArray = [];
let isNullInterpreted = false;
const output = array1.reduce(function (acc, curr, index) {
  isNullInterpreted = isNullInterpreted || curr == null;
  return resultArray[index] = isNullInterpreted ? null : acc   curr;
}, 0);
console.log(resultArray);
console.log(output);

解釋 null 后停止迭代回圈

const array1 = [-12.66, 268.2, 48.99, -1264.5, 20550, 91.2, 0, 0, 0, 0, 0, 0, 0, 0, 9235.5, 1500, 0, 0, 18.99, 0, 0, null, null, null, null, null, null, null, null, null, null];
let resultArray = [];
let isNullInterpreted = false;
const output = array1.reduce(function (acc, curr, index) {
  isNullInterpreted = isNullInterpreted || curr == null;
  if (!isNullInterpreted) {
    resultArray[index] = acc   curr;
  }
  return resultArray[resultArray.length - 1]
}, 0);
console.log(resultArray);
console.log(output);

標籤：javascript ecmascript-6

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