以 YYYY-MM-DD 格式从数组中获取上个月的所有记录

Question

How can I find all objects in array [{value:"String", date:"YYYY-MM-DD"}] with the last provided month and year of course?Year range is 2018-2020. I want something instead of slicing and equaling.

For example, i got: 50 items array with value and date property. Value is simple price in string format and date is like "2020-02-12", "2019-12-13", "2019-04-28" and so on. So I need to get all values from the last month and sum them.So the problem is in the finding last month. Array is dynamic, that means that I got like 300 variation of the array, as a result last month and year each time could be different.

Answer 1

As I mentioned in the comment section, you can convert each strings which has date values with new Date() then using .filter() on the array would do the job.

See the following example:

 const data = [{value: 'val3', date: '2017-05-06'},{value: 'val2', date: '2018-05-06'},{value: 'val1', date: '1988-05-06'},{value: 'val4', date: '2019-03-22'},{value: 'val6', date: '2019-12-24'}]; const result = data.filter(e => new Date('2018-01-01') < new Date(e.date) && new Date(e.date) < new Date('2020-01-01') ); console.log(result);

I hope this helps!

Answer 2

as I understand it, you need the sum of all the values for the last month. I think the code below is what you need:

 let data = [{value: '43.21', date: '2019-07-06'},{value: '24.34', date: '2017-03-03'},{value: '54.32', date: '2020-02-03'},{value: '11.32', date: '2020-02-05'},{value: '34.23', date: '2019-11-21'},{value: '32.34', date: '2020-01-24'},{value: '32.34', date: '2020-02-21'}]; //find last newest record to get it's date let lastdate=new Date(data.reduce(function (a, b) { return a.date > b.date ? a : b; }).date); let result = data.reduce(function(sum, e){ return (isNaN(parseFloat(sum))?0:parseFloat(sum))+(new Date(lastdate.getFullYear(), lastdate.getMonth(), 1) < new Date(e.date) && new Date(e.date) <= new Date(lastdate.getFullYear(), lastdate.getMonth() + 1, 0)?parseFloat(e.value):0) }); document.write("last year/month: " + lastdate.getFullYear()+"/"+(lastdate.getMonth()+1)); document.write("<br>result: "+ result);

Answer 3

Given the a date format of YYYY-MM-DD, the values will sort and compare lexically. So first find the last month, then filter for dates in that month, eg

 let data = [ {a:'a', date:'2020-02-12'}, {a:'a', date:'2019-12-13'}, {a:'a', date:'2019-04-28'}, {a:'a', date:'2019-12-15'}, {a:'a', date:'2020-02-28'}, {a:'a', date:'2018-12-13'}]; // Get last date let last = data.map(obj => obj.date).sort()[data.length-1]; console.log(last); // Get objects in last month let lastMonthsValues = data.filter( obj => obj.date.substr(0,7) == last.substr(0,7) ); // Last month's objects console.log(lastMonthsValues);

You could do the same thing using Date objects, but that requires firstly parsing to Date, then comparing using date.getUTCFullYear() and date.getUTCMonth() instead of simple string operations.

 let data = [ {a:'a', date:'2020-02-12'}, {a:'a', date:'2019-12-13'}, {a:'a', date:'2019-04-28'}, {a:'a', date:'2019-12-15'}, {a:'a', date:'2020-02-28'}, {a:'a', date:'2018-12-13'}]; // Get last date let last = data.map(obj => obj.date).sort((a, b) => new Date(a) - new Date(b))[data.length-1]; console.log(last); // Get objects in last month let lastMonthsValues = data.filter(obj => { let d0 = new Date(last); let d1 = new Date(obj.date); return d1.getUTCFullYear() == d0.getUTCFullYear() && d1.getUTCMonth() == d0.getUTCMonth(); } ); // Last month's objects console.log(lastMonthsValues);

Using string methods is much less code and likely very much more efficient.

Answer 4

I did myself something like this:

info.incomes.sort(function(a, b) {
    return new Date(b.date)-new Date(a.date);
});
let comparison =[];
for (let i in info.incomes){    
comparison.push(info.incomes[i].date.substr(0, 7));
}
let lastmonth = 0;
for (let i in comparison){
    if (comparison[0] === comparison[i]){        
        lastmonth+=parseFloat(info.incomes[i].value);
    }      
}

I just need last month incomes to be summarized, so i just sorted them, and checked if they equals to my last date. Sorry for bad variables naming =)