Duplicate check for comma separated array

Question

I am trying to check duplicate in the following array, just i am want to return true or false if duplicate exists.

var array = ["Saturday", "Sunday", "Monday", "Tuesday", "Saturday" ];

for ( var i = 0; i < array.length; i++){

for (var j = i+1; j< array.length; j++){

if (array [i] === array [j]){

console.log(array[i]);
}
}

}

I tried the above , it giving result only for one item in an array not for comma separated. How i can write a duplicate check function in best way for comma separated array?

Array(10)
 0: "test3,tier 1,test,test2
"1: "test3,tier 1,test,test2
"2: "test3,tier 1,test,test2
"3: "test3,tier 1,test,test2
"4: "test3,tier 1,test,test2
"5: "test3,tier 1,test,test2
"6: "test3,tier 1,test,test2
"7: "test3,tier 1,test,test2
"8: "test3,tier 1,test,test2
"9: "test3,tier 1,test,test2
"length: 10
__proto__: Array(0)

oh, so your real array has string values that have commas in them, they're just strings, the commas mean nothing special - so what do you want to test exactly? the code will check and output the duplicates (i.e. all 10 are the same) — Jaromanda X
– Jaromanda X, Commented Jul 31, 2018 at 9:56
i just want to return true if not duplicates and false for duplicate exists — SmartestVEGA
– SmartestVEGA, Commented Jul 31, 2018 at 9:58
so, return true where you console.log ... return false outside of the loops — Jaromanda X
– Jaromanda X, Commented Jul 31, 2018 at 10:00
new Set(array).size === array.length is true if all array items are unique — Jaromanda X
– Jaromanda X, Commented Jul 31, 2018 at 10:03
a.map(item=> item .split(',').map(child => child)).map(item => new Set(item).size === item.length) try by doing this may be this solves your problem — Shorya Vaish
– Shorya Vaish, Commented Jul 31, 2018 at 10:18

Hossam Houssien · Accepted Answer · 2020-04-22 09:39:29Z

3

The items in a Set will always be unique, as it only keeps one copy of each value you put in. Here's a function that uses this property:

function hasDuplicates(iterable) {
  return  new Set(iterable).size !== iterable.length;
}

// Demo
var array = ["Saturday", "Sunday", "Monday", "Tuesday", "Saturday" ];
console.log(hasDuplicates(array))

// Returns True if there is duplicates
// Otherwise return false

Set(iterable).size will return the count of unique elements in that set, while iterable.length is the counts of all elements in the original array.

Edit #1

To check ONLY the first item for duplicates you can use something like this

var array = ["Saturday",  "Saturday", "Sunday", "Monday", "Tuesday" ];


console.log(array.indexOf(array[0] , 1) === -1 ? "No duplicates" : "Has duplicate" );

edited Apr 22, 2020 at 9:39

answered Jul 31, 2018 at 10:29

Hossam Houssien

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5 Comments

SmartestVEGA Over a year ago

i need to check only first value of comma separated values for each item in the array for duplicates

SmartestVEGA Over a year ago

please consider the second array in the question

Hossam Houssien Over a year ago

Which second array? there is only one in your question!

SmartestVEGA Over a year ago

Array(10) 0: "test3,tier 1,test,test2 "1: "test3,tier 1,test,test2 "2: "test3,tier 1,test,test2 "3: "test3,tier 1,test,test2 "4: "test3,tier 1,test,test2 "5: "test3,tier 1,test,test2 "6: "test3,tier 1,test,test2 "7: "test3,tier 1,test,test2 "8: "test3,tier 1,test,test2 "9: "test3,tier 1,test,test2 "length: 10

SmartestVEGA Over a year ago

Thanks for helping, i made the final solution here as another answer

SmartestVEGA · Accepted Answer · 2018-07-31 11:54:37Z

0

// Check duplicates in upload data excel

    checkDuplicates(arr) {

        if (arr.length > 1) {
            for (var i = 0; i < arr.length; i++) {
                for (var j = i + 1; j < arr.length; j++) {

                    if (arr[i].split(',')[0] === arr[j].split(',')[0]) {
                        return true;
                    } else {
                        return false;
                    }
                }
            }
        } else {
            return false;
        }
    }

answered Jul 31, 2018 at 11:54

SmartestVEGA

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