Find index and value of item with latest date-CodePudding

My API structure

let datas = [{
  end_date: '2019-12-16'
}, {
  end_date: '2018-12-16'
}];
let latestData = datas.filter( /* I need an index number of item based on latest date */ );

Looking for vanilla JavaScript code

CodePudding user response：

Try to use .sort().

If you sort the array in order of recent date, the most recent date will come first in the array. It is recommended to use .sort().

const datas = [{end_date: '2018-12-16'}, {end_date: '2020-12-16'}, {end_date: '2019-12-16'}, {end_date: '2017-12-16'} ];
const latestData = datas.sort((a, b) => {
  return new Date(b.end_date) - new Date(a.end_date);
});
console.log(latestData[0]); // {end_date: '2020-12-16'}

Edit.

If you want to get only index of origin array.

const datas = [{end_date: '2018-12-16'}, {end_date: '2020-12-16'}, {end_date: '2019-12-16'}, {end_date: '2017-12-16'} ];
const timestamps = datas.map((obj) => {
  return  new Date(obj.end_date);
});
const latest =  new Date(Math.max(...timestamps));
const latestDataIndex = timestamps.indexOf(latest);

console.log(datas[latestDataIndex]);

Plus.

You can use for loop to browse array only once without sorting it.

const datas = [{end_date: '2018-12-16'}, {end_date: '2020-12-16'}, {end_date: '2019-12-16'}, {end_date: '2017-12-16'}, {end_date: '2021-12-16'} ];
let minDate = datas[0];
let index = 0;
for (let i = 0; i < datas.length; i  ) {
  const currentData = datas[i];
  if (new Date(minDate.end_date) < new Date(currentData.end_date)) {
    minDate = currentData;
    index = i;
  }
}
console.log(datas[index]);

CodePudding user response：

There is no need to sort (snark removed). Iterate the array and keep track of the index that contains the largest value. Here is an implementation using Array.reduce:

let datas = [{
  end_date: '2018-12-16'
}, {
  end_date: '2020-12-16'
}, {
  end_date: '2019-12-16'
}, {
  end_date: '2017-12-16'
}];
let index = datas.reduce((retval, item, index, array) => retval === -1 || array[retval].end_date < item.end_date ? index : retval, -1);
console.log(index);

CodePudding user response：

You can use Array.sort() with localeCompare() to compare the strings

let datas = [ 
    {
        end_date: '2019-12-16' 
},
    {
    end_date: '2019-12-16' 
    },
    {
    end_date: '2022-12-16' 
    }
]

const res = datas.map((date, i)=>(date.i=i, date)).sort((a,b)=>{
    return  b.end_date.localeCompare(a.end_date);
})

console.log(res[0]);

Alternativelyyou you can use an more performant Array.reduce() approach.

let datas = [ { end_date: '2019-12-16' }, { end_date: '2019-12-16' }, { end_date: '2022-12-16' } ]

const r=datas.reduce((acc, curr, i)=>{
    if(Object.keys(acc).length === 0){
        return {...curr, i: i};
    }else if(new Date(acc.end_date) < new Date(curr.end_date)){
       return {...curr, i: i};
    }else return acc;
},{});

console.log(r);

CodePudding user response：

You can use Math.max but unix time required

Math.max.apply(Math, array.map(function(o) { return o.end_date; }))