Delete duplicate elements from Array in Javascript [duplicate]

Answer 1

Use Array.prototype.filter to filter out the elements and to keep a check of duplicates use a temp array

var newarray = [{
  Email: "test1@gmail.com",
  ID: "A"
}, {
  Email: "test2@gmail.com",
  ID: "B"
}, {
  Email: "test3@gmail.com",
  ID: "A"
}, {
  Email: "test4@gmail.com",
  ID: "C"
}, {
  Email: "test5@gmail.com",
  ID: "C"
}];
   
// Array to keep track of duplicates
var dups = [];
var arr = newarray.filter(function(el) {
  // If it is not a duplicate, return true
  if (dups.indexOf(el.ID) == -1) {
    dups.push(el.ID);
    return true;
  }

  return false;
  
});

console.log(arr);

Answer 2

Another solution using Array.prototype.reduce and a hash table - see demo below:

var newarray=[ { Email:"test1@gmail.com", ID:"A" }, { Email:"test2@gmail.com", ID:"B" }, { Email:"test3@gmail.com", ID:"A" }, { Email:"test4@gmail.com", ID:"C" }, { Email:"test5@gmail.com", ID:"C" } ];

var result = newarray.reduce(function(hash){
  return function(prev,curr){
     !hash[curr.ID] && (hash[curr.ID]=prev.push(curr));
     return prev;
  };
}(Object.create(null)),[]);

console.log(result);

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Answer 3

You could filter it with a hash table.

var newarray = [{ Email: "test1@gmail.com", ID: "A" }, { Email: "test2@gmail.com", ID: "B" }, { Email: "test3@gmail.com", ID: "A" }, { Email: "test4@gmail.com", ID: "C" }, { Email: "test5@gmail.com", ID: "C" }],
    filtered = newarray.filter(function (a) {
        if (!this[a.ID]) {
            this[a.ID] = true;
            return true;
        }
    }, Object.create(null));

console.log(filtered);

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ES6 with Set

var newarray = [{ Email: "test1@gmail.com", ID: "A" }, { Email: "test2@gmail.com", ID: "B" }, { Email: "test3@gmail.com", ID: "A" }, { Email: "test4@gmail.com", ID: "C" }, { Email: "test5@gmail.com", ID: "C" }],
    filtered = newarray.filter((s => a => !s.has(a.ID) && s.add(a.ID))(new Set));

console.log(filtered);

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Answer 4

If you can use Javascript libraries such as underscore or lodash, I recommend having a look at _.uniq function in their libraries. From lodash:

_.uniq(array, [isSorted=false], [callback=_.identity], [thisArg])

Here you have to use like below,

var non_duplidated_data = _.uniq(newarray, 'ID');