如何在共享同一字段的二维数组中累积所有值

Question

我有一个2D数组，它包含这样的值：

var array = [["10/10/2020","1000"],["10/10/2020","300"],["07/10/2020","100"],["07/10/2020","100"],["03/10/2020","100"],["10/10/2020","100"]];

对于每个具有相同日期值(第一个元素)的嵌套数组，我想把第二个值加起来，得到这样的值：

arrayAdd = [["10/10/2020","1400"],["O7/10/2020","200"],["03/10/2020","100"]]

我该怎么做？

Answer 1

var array = [["10/10/2020","1000"],["10/10/2020","300"],["07/10/2020","100"],["07/10/2020","100"],["03/10/2020","100"],["10/10/2020","100"]];
function fromEntries (iterable) {
return [...iterable].reduce((obj, [key, val]) => {
obj[key] = String(obj[key] ? +obj[key] + +val : val)
return obj
}, {})
}
console.log(fromEntries(array))

Answer 2

逐步：

1. 创建一个空对象/贴图。

2. 遍历你的数组。

   获取数组中每个项的第一个元素(日期)，并检查该键是否已在对象中。

   • 如果不是，则添加它。该值将是第二个元素(数字)。

   • 如果它已经存在，则递增该值。

3. Object.entries会将该对象变成一个具有所需形状的数组，如下所示：

const obj = {
"10/10/2020": "1400",
"O7/10/2020": "200",
"03/10/2020": "100",
};
console.log(Object.entries(obj));

.as-console-wrapper {
max-height: 100% !important;
}

这应该有助于你开始。

Answer 3

您可以执行此

const data = [["10/10/2020","1000"],["10/10/2020","300"],["07/10/2020","100"],["07/10/2020","100"],["03/10/2020","100"],["10/10/2020","100"]];
const result = Object.entries(data.reduce((res, [key, value] ) => {
return {
...res,
[key]: (res[key] || 0) + Number(value)
}
}, {}))
console.log(result)

Answer 4

有几种方法可以处理这个问题。

您可以比较每个日期的字符串值以查看它们是否相同，也可以将它们转换为日期对象并以这种方式进行比较。这里有一个指向MDN文档的链接，它显示了如何获得日期的基元值。

我将使用字符串值，因为在这种情况下，我将假设所有日期都以一致的格式出现。

let array = [["10/10/2020","1000"],["10/10/2020","300"],["07/10/2020","100"],["07/10/2020","100"],["03/10/2020","100"],["10/10/2020","100"]];
let arrayAdd = []
for (let valuePair of array) {
// grab just the date value
let date = valuePair[0];
// check to see if pair is in arrayAdd 
let foundPair = arrayAdd.find(el => el[0] === date)
// will return undefined if nothing found
if (!foundPair) {
// if nothing found, we push the entire value and date pair
arrayAdd.push(valuePair);
} else {
// few things happening here.. 
// we have to convert each value to number to properly add
// once they're added, we convert that new value back into a string
// and then set the value of the found pair to that new string.
foundPair[1] = (Number(valuePair[1]) + 
Number(foundPair[1])).toString();
}
}
console.log(arrayAdd);