Get unique datetime string value from array of arrays in javascript

Question

I want to loop over an array of arrays structure in order to filter out the duplicate datetime string values, and push the unique datetime string values sorted in a new array. I have tried to use a nested forEach() method in order to compare each current key value with all the key values inside the array arr, and push them inside the res array in case of non matching situation, but it seems not working properly.

Here the array of arrays structure

arr =[
   ["some_value", "2016-11-23 18:11", 1]
   ["some_value", "2016-11-23 18:01", 1]
   ["some_value", "2016-11-23 18:01", 2]
   ["some_value", "2016-11-23 18:01", 1]
   ["some_value", "2016-11-23 18:22", 1]
   ["some_value", "2016-11-23 18:23", 1]
   ["some_value", "2016-11-23 18:25", 1]
   ["some_value", "2016-11-23 18:24", 3]
   ["some_value", "2016-11-23 18:26", 1]
   ["some_value", "2016-11-23 18:27", 1]
];

What I want to obtain as result

res = ["2016-11-23 18:01",
       "2016-11-23 18:11", 
       "2016-11-23 18:22",
       "2016-11-23 18:23",
       "2016-11-23 18:24",
       "2016-11-23 18:25",
       "2016-11-23 18:26",
       "2016-11-23 18:27"];

Can someone give me some tips on order to understand how to proceed?

maioman · Accepted Answer · 2017-11-23 17:36:32Z

3

I would map the array of arrays to just an array of date strings:

arr = arrayOfArrays.map(x => x[1])

then if you convert it to set you get unique values

var set = new Set(arr)

if needed you can eventually turn it back to array

var uniq = Array.from(set)

for sorting

uniq.sort((a,b)=> new Date(a) - new Date(b))

var arrayOfArrays = [
   ["some_value", "2016-11-23 18:11", 1],
   ["some_value", "2016-11-23 18:01", 1],
   ["some_value", "2016-11-23 18:01", 2],
   ["some_value", "2016-11-23 18:01", 1],
   ["some_value", "2016-11-23 18:22", 1],
   ["some_value", "2016-11-23 18:23", 1],
   ["some_value", "2016-11-23 18:25", 1],
   ["some_value", "2016-11-23 18:24", 3],
   ["some_value", "2016-11-23 18:26", 1],
   ["some_value", "2016-11-23 18:27", 1],
];

var arr = arrayOfArrays.map(x => x[1])
var set = new Set(arr)

var uniq = Array.from(set)

uniq.sort((a,b)=> new Date(a) - new Date(b))

console.log(uniq)

edited Nov 23, 2017 at 17:36

answered Nov 23, 2017 at 17:29

maioman

18.8k4 gold badges39 silver badges46 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

UgoL Over a year ago

In this specific circumstance what a and b stand for in the .sort() method? Since in the moz documentation it refers to 2 parameter values to compare with. I have tried to console.log the result of datetime differences and I didn't exactly get the point.

maioman Over a year ago

a and b represent two elements of the array, if the function returns something below 0 a is ordered before b, otherwise after

maioman Over a year ago

glad I could help

Community · Accepted Answer · 2020-06-20 09:12:55Z

A solution using `map` and `Set`

You can map over the array to pluck the dates:

const dates = arr.map(item => item[1]);

then you can put them in a new Set which is an array that holds only unique items. calling .values on the created set will return its results.

arr = [
   ["some_value", "2016-11-23 18:11", 1],
   ["some_value", "2016-11-23 18:01", 1],
   ["some_value", "2016-11-23 18:01", 2],
   ["some_value", "2016-11-23 18:01", 1],
   ["some_value", "2016-11-23 18:22", 1],
   ["some_value", "2016-11-23 18:23", 1],
   ["some_value", "2016-11-23 18:25", 1],
   ["some_value", "2016-11-23 18:24", 3],
   ["some_value", "2016-11-23 18:26", 1],
   ["some_value", "2016-11-23 18:27", 1],
];


const dates = arr.map(item => item[1]);
const result = new Set(dates);

console.log('result: ', Array.from(result))

Learn more!

You can read more about sets here on MDN

Here is an image to better conceptualize the idea of the "functional style" map/filter/reduce array functions (filter is where you'd ommit the onions):

Image Source: https://twitter.com/francesc/status/507942534388011008

nmfzone · Accepted Answer · 2017-11-23 18:22:03Z

1

I just want to answer with the helper of lodash. I just believe this is still relevant.

var arr =[
    ["some_value", "2016-11-23 18:11", 1],
    ["some_value", "2016-11-23 18:01", 1],
    ["some_value", "2016-11-23 18:01", 2],
    ["some_value", "2016-11-23 18:01", 1],
    ["some_value", "2016-11-23 18:22", 1],
    ["some_value", "2016-11-23 18:23", 1],
    ["some_value", "2016-11-23 18:25", 1],
    ["some_value", "2016-11-23 18:24", 3],
    ["some_value", "2016-11-23 18:26", 1],
    ["some_value", "2016-11-23 18:27", 1]
];

_.map(_.sortBy(_.uniqBy(arr, v => v[1]), v => v[1]), v => v[1]);

edited Nov 23, 2017 at 18:22

answered Nov 23, 2017 at 18:15

nmfzone

2,9431 gold badge23 silver badges34 bronze badges

1 Comment

UgoL Over a year ago

Interesting library.. I'll take a look! Thanks

Danish · Accepted Answer · 2017-11-23 17:39:26Z

0

        var arr = arr = [
        ["some_value", "2016-11-23 18:11", 1],
        ["some_value", "2016-11-23 18:01", 1],
        ["some_value", "2016-11-23 18:01", 2],
        ["some_value", "2016-11-23 18:01", 1],
        ["some_value", "2016-11-23 18:22", 1],
        ["some_value", "2016-11-23 18:23", 1],
        ["some_value", "2016-11-23 18:25", 1],
        ["some_value", "2016-11-23 18:24", 3],
        ["some_value", "2016-11-23 18:26", 1],
        ["some_value", "2016-11-23 18:27", 1],
     ];
    var dates = arr.map(x => x[1])
    var uniqueArray = dates.filter(function (item, pos) {
        return dates.indexOf(item) == pos;
    });

answered Nov 23, 2017 at 17:39

Danish

5965 silver badges14 bronze badges

Comments

Dhaval Panara · Accepted Answer · 2017-11-23 17:50:46Z

You can try below code to get your desired output.

function onlyUnique(value, index, self) { 
  return self.indexOf(value) === index;
}

var arr =[
  ["some_value", "2016-11-23 18:11", 1],
  ["some_value", "2016-11-23 18:01", 1],
  ["some_value", "2016-11-23 18:01", 2],
  ["some_value", "2016-11-23 18:01", 1],
  ["some_value", "2016-11-23 18:22", 1],
  ["some_value", "2016-11-23 18:23", 1],
  ["some_value", "2016-11-23 18:25", 1],
  ["some_value", "2016-11-23 18:24", 3],
  ["some_value", "2016-11-23 18:26", 1],
  ["some_value", "2016-11-23 18:27", 1]
];

var rest = [];


arr.forEach(function(entry) {

rest.push(entry[1]) 
});

rest.sort();

var finalArr = rest.filter( onlyUnique );

console.log(finalArr);

Collectives™ on Stack Overflow

Get unique datetime string value from array of arrays in javascript

5 Answers 5

3 Comments

A solution using `map` and `Set`

Learn more!

Comments

1 Comment

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

3 Comments

A solution using map and Set

Learn more!

Comments

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related

A solution using `map` and `Set`