Remove duplicates from array of arrays by the first object

Question

I have an array of arrays which looks like this:

arr = [
["Bob","USA","55"],
["Frank","Canada","20"],
["Bob","UK","35"],
["Bob","France","38"],
["Anna","Poland","22"]
]

I like to remove duplicate arrays which have the same value on the first position(the same name) - so I'd like to my output will look like that:

arr = [
["Bob","USA","55"],
["Frank","Canada","20"],
["Anna","Poland","22"]
]

I'm trying to do this in this way:

uniqueArr = []
for (var i in arr) {
if (uniqueArr.indexOf(arr[i][0]) === -1)) {
uniqueArr.push(arr[i][0])
}

Everything works ok - my output looks like Bob, Frank, Anna

But the problem is when I'm trying to recive whole arrays with unique value name. When I'm doing:

uniqueArr = []
for (var i in arr) {
if (uniqueArr.indexOf(arr[i][0]) === -1)) {
uniqueArr.push(arr[i])
}

My output looks exactly like the input array. Do you know where I'm doing wrong?

The problem is when you push the entire array onto uniqueArr, you can't just use indexOf on it any more because it no longer contains simple strings. — CodingIntrigue
– CodingIntrigue, Commented May 28, 2015 at 12:00

CodingIntrigue · Accepted Answer · 2015-05-28 12:03:41Z

4

You could keep track of the key string in a separate array and track that instead, for example:

var uniqueArr = [],
    keys = []; // Create an array for storing the key values
for (var i in arr) {    
    if (keys.indexOf(arr[i][0]) === -1) {
        uniqueArr.push(arr[i]); // Push the value onto the unique array
        keys.push(arr[i][0]); // Push the key onto the 'key' array
    }
}
console.log(uniqueArr);

jsFiddle example

answered May 28, 2015 at 12:03

CodingIntrigue

79k32 gold badges176 silver badges178 bronze badges

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

Comments

Balachandran · Accepted Answer · 2015-05-28 12:11:49Z

0

try

arr = [
    ["Bob", "USA", "55"],
    ["Frank", "Canada", "20"],
    ["Bob", "UK", "35"],
    ["Bob", "France", "38"],
    ["Anna", "Poland", "22"]
]
var newArr = [];
for (var i = 0; i < arr.length; i++) {
    if (isInArr(newArr, arr[i]) == -1) {
        newArr.push(arr[i]);
    }
}

function isInArr(checkArr, value) {
    var index = -1;
    for (var i = 0; i < checkArr.length; i++) {
        if (checkArr[i][0] == value[0]) {
            index = i;
            break;
        }
    }
    return index;
}

console.log(newArr)

DEMO

edited May 28, 2015 at 12:11

answered May 28, 2015 at 12:04

Balachandran

9,6271 gold badge19 silver badges26 bronze badges

Comments

Victor · Accepted Answer · 2015-05-28 12:11:53Z

Take a look atthe function unique2. It works!

originalArr = [
  ["Bob", "USA", "55"],
  ["Frank", "Canada", "20"],
  ["Bob", "UK", "35"],
  ["Bob", "France", "38"],
  ["Anna", "Poland", "22"]
];

function unique(arr) {
  uniqueArr = [];
  for (var i in arr) {
    if (uniqueArr.indexOf(arr[i][0]) === -1) {
      uniqueArr.push(arr[i]);
    }
  }
  return uniqueArr;
}

function unique2(arr) {
  uniqueArr = [];
  keys = [];
  for (var i in arr) {
    if (keys.indexOf(arr[i][0]) === -1) {
      uniqueArr.push(arr[i]);
      keys.push(arr[i][0]);
    }
  }
  return uniqueArr;
}



var response = document.getElementById('response');
response.textContent = JSON.stringify(unique(originalArr));

var response2 = document.getElementById('response2');
response2.textContent = JSON.stringify(unique2(originalArr));

<h1>Your code</h1>
<div id="response"></div>

<h1>My code</h1>
<div id="response2"></div>

Collectives™ on Stack Overflow

Remove duplicates from array of arrays by the first object

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related