Check for duplicate values in array of objects in angular2

Try this.

reduce(){
   let res=[];
   this.traveler.map(function(item){
     var existItem = res.find(x=>x.description==item.description);
     if(existItem)
      console.log("item already exist");
     else
      res.push(item);
   });
   console.log(res);
 }

remove reduce and use only filter.

let existItem = traveler.filter(item => item.description === obj.description);
if (existItem.length > 1) {
    return this.toaster.pop('info', 'Insertion unsuccessful', 'Duplicate answer found')
}

You can write the code:

var traveler = [
  {
    description: "Senior",
    Amount: 50
  },
  {
    description: "Senior",
    Amount: 10
  },
  {
    description: "Adult",
    Amount: 75
  },
  {
    description: "Child",
    Amount: 35
  },
  {
    description: "Infant",
    Amount: 25
  },
  {
    description: "Adult",
    Amount: 105
  }
];

function hasDuplicateDesc(collection) {
  var groups = collection.reduce((acc, cur) => {
    acc[cur.description] = (acc[cur.description] || 0) + 1;
    return acc;
  }, {});

  return Object.values(groups).some(num => num > 1);
}

if (hasDuplicateDesc(traveler)) {
  return this.toaster.pop(
    "info",
    "Insertion unsuccessful",
    "Duplicate answer found"
  );
}

groups is an object which basically creates an object:

{
  "Senior": 2,
  "Adult": 2,
  "Child": 1,
  "Infant": 1
}

We grab the values the object using Object.values(groups), and check if there is a single number which is grater than 1. If exists any num > 1, then we can say duplicate description is present.

The control is not going inside the if block because you're not pushing anything into acc (and you didn't initialized it in the last argument of reduce), the reduce operation won't do it for you.

This solution should work:

var res = traveler.reduce((acc, obj)=> {
    var existItem = acc.find(item => item.description === obj.description);
    if(existItem) {
        return this.toaster.pop(
            'info', 'Insertion unsuccessful', 'Duplicate answer found'
        );
    }
    acc.push(obj);
    return acc;
}, []);

With this res will contain unique values and you will be notified of duplicates with your toaster.pop. But you can also keep the duplicates by pushing into a duplicateList inside your if block.

here iam trying to figure it out duplicate emails in the array. i have enteredEmails array which is having the list of emails which may unique or duplicate.

please find the below example.

this.enteredEmails.forEach(emailItr => {

      matchedEmail = [];
      matchedEmail = this.enteredEmails.filter((val) => val.emailId === emailItr.emailId);

      if (matchedEmail.length > 1) {
        return this.isDuplicate = true;

      }

    });

}