查找js数组中缺少的月份

Question

我有以下数组

[
{ Month: '2021-05', Count: 36 },
{ Month: '2021-06', Count: 1048 },
{ Month: '2021-07', Count: 572 },
{ Month: '2021-09', Count: 3 },
{ Month: '2021-12', Count: 52 },
{ Month: '2022-01', Count: 4 },
{ Month: '2022-02', Count: 273 },
{ Month: '2022-04', Count: 96 }
]

我错过了几个月。我知道需要多少个月(可能是12个月，也可能是更多或更少)，我需要将缺失的月份(如本例中的2021-08)添加为0计数。怎么做呢?

Answer 1

这是一个纯粹的函数式方法，它将用new项创建一个new数组，并按顺序插入所有缺失的月份。该代码包括一些解释过程的注释:

const parseDate = str => str.split('-').map(Number);
const formatDate = (year, month) => `${year}-${String(month).padStart(2, '0')}`;
function createContinuousMonthCounts (array) {
const all = [];
// get initial year/month values from first item
let [year, month] = parseDate(array[0].Month);
const advanceDate = () => {
month += 1;
if (month > 12) {
year += 1;
month = 1;
}
};
for (const item of array) {
const [y, m] = parseDate(item.Month);
// while the current month is not equal to the current item's month,
// create an entry for the month, append it, and advance to the next month
while (year !== y || month !== m) {
all.push({Month: formatDate(year, month), Count: 0});
advanceDate();
}
// after we're up to date, add the current item and advance the date
all.push({...item});
advanceDate();
}
return all;
}
const array = [
{ Month: '2021-05', Count: 36 },
{ Month: '2021-06', Count: 1048 },
{ Month: '2021-07', Count: 572 },
{ Month: '2021-09', Count: 3 },
{ Month: '2021-12', Count: 52 },
{ Month: '2022-01', Count: 4 },
{ Month: '2022-02', Count: 273 },
{ Month: '2022-04', Count: 96 },
];
const all = createContinuousMonthCounts(array);
for (const {Month, Count} of all) console.log(Month, Count);

Answer 2

只是一个进入黑暗的镜头(请考虑在您的问题中添加一些代码):

const months = [
{ Month: '2021-05', Count: 36 },
{ Month: '2021-06', Count: 1048 },
{ Month: '2021-07', Count: 572 },
{ Month: '2021-09', Count: 3 },
{ Month: '2021-12', Count: 52 },
{ Month: '2022-01', Count: 4 },
{ Month: '2022-02', Count: 273 },
{ Month: '2022-04', Count: 96 }
];
const neededMonths = [
"2021-01","2021-02","2021-03","2021-04","2021-05","2021-06","2021-07","2021-08","2021-09","2021-10","2021-11","2021-12"
]
const missedMonths = [];
months.map( m => {
if(neededMonths.indexOf(m.Month) == -1 ){
missedMonths.push(m.Month);
}
});
console.log(missedMonths);

Answer 3

您首先需要一个方法来查找范围之间的所有月份，然后遍历所有月份并使用count: 0添加缺失的月份:

const months = [
{ Month: '2021-05', Count: 36 },
{ Month: '2021-06', Count: 1048 },
{ Month: '2021-07', Count: 572 },
{ Month: '2021-09', Count: 3 },
{ Month: '2021-12', Count: 52 },
{ Month: '2022-01', Count: 4 },
{ Month: '2022-02', Count: 273 },
{ Month: '2022-04', Count: 96 }
]
const firstMonth = months.at(0).Month;
const lastMonth = months.at(-1).Month;
const [initialYear, initialMonth] = firstMonth.split('-');
const [endingYear, endingMonth] = lastMonth.split('-');
const allMonths = [];
let currentMonth = initialMonth;
let currentYear = initialYear;
while (`${currentYear}-${(''+currentMonth).padStart(2, '0')}` !== lastMonth) {
allMonths.push(`${currentYear}-${(''+currentMonth).padStart(2, '0')}`);
currentMonth++;
if (currentMonth === 13) {
currentMonth = 1;
currentYear++;
}
}
allMonths.forEach(month => {
if (!months.find(m => m.Month === month)) {
months.push({Month: month, count: 0});
}
});
console.log(months);