Question

135

How do I make an array with unique elements (i.e. remove duplicates)?

rated 0 times [ 141] [ 6] / answers: 1 / hits: 85526 / 13 Years ago, thu, august 4, 2011, 12:00:00

I have this code:

var ar = [10,7,8,3,4,7,6];



function isin(n,a){

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

    if (a[i]== n) {

      var b = true;

      return b;

    } else {

      var c = false;

      return c;

   }

  }

}



function unique(a){

  var arr = [];

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

    if (!isin(a[i],arr)){

      arr.push(a[i]);

    }

  }



 return arr;

}



alert(unique(ar));

In this code, I try to create new unique array (without duplicates) out of the original one.
But I still get the original array! Where's my mistake?

Answers

Only authorized users can answer the question. Please sign in first, or register a free account.

quentinaveryb

Add To Favorites

Follow

Total Points: 102

Total Questions: 100

Total Answers: 93

Location: Colombia

Member since Mon, May 2, 2022

2 Years ago

quentinaveryb questions

1 How to use annotation layer in PDF.js?

Thu, Aug 6, 20, 00:00, 4 Years ago

1 Cannot assign to read only property of #< Object> using React with Recoil

Sat, Jul 18, 20, 00:00, 4 Years ago

1 Strapi JWT token lifetime?

Fri, Jul 17, 20, 00:00, 4 Years ago

1 What is the difference between async await and a regular fetch?

Tue, Feb 4, 20, 00:00, 4 Years ago

1 How do I include a JavaScript variable in an HTML header?

Mon, Aug 12, 19, 00:00, 5 Years ago

View All

answered 13 Years ago lindsay · Accepted Answer

Using a plain array and returning the keys of associative array (containing only the unique values from given array) is more efficient:

function ArrNoDupe(a) {

    var temp = {};

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

        temp[a[i]] = true;

    var r = [];

    for (var k in temp)

        r.push(k);

    return r;

}



$(document).ready(function() {

    var arr = [10, 7, 8, 3, 4, 3, 7, 6];

    var noDupes = ArrNoDupe(arr);

    $(#before).html(Before:  + arr.join(, ));

    $(#after).html(After:  + noDupes.join(, ));

});

<script src=https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js></script>

<div id=before></div>

<div id=after></div>

Note: The function does not preserve the order of the items, so if this is important use different logic.

As of IE9 and on all other modern browsers (e.g. Chrome, Firefox) this can become even more efficient by using the Object.keys() method:

function ArrNoDupe(a) {

    var temp = {};

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

        temp[a[i]] = true;

    return Object.keys(temp);

}



$(document).ready(function() {

    var arr = [10, 7, 8, 3, 4, 3, 7, 6];

    var noDupes = ArrNoDupe(arr);

    $(#before).html(Before:  + arr.join(, ));

    $(#after).html(After:  + noDupes.join(, ));

});

<script src=https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js></script>

<div id=before></div>

<div id=after></div>

_{Thanks wateriswet for bringing this to my attention. :)}