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JavaScript

Posted by michael singh
michael singh
5,927 Points

How to return a certain value from an array

I am trying to create a function that return an integer that only appears once in an array. For example:

var arr = [1 , 1, 2, 3, 3,];

The function would return the value 2 as it only appears once.

This is what I have so far but I feel I am very off

function singleInteger(arr){
          for(var i = 0; i < arr.length; i+=1)
                 if(arr[i].indexOf() > 1){
                        return arr[i];
                         }
}
tobiaskrause
tobiaskrause
9,160 Points

I dont have the time yet to write your code...but this should help you http://stackoverflow.com/questions/840781/easiest-way-to-find-duplicate-values-in-a-javascript-array

Matt F.
Matt F.
9,518 Points

Do you have a reason to do this? Would you like it to return all values that only appear once - or will your arrays each only have one number that appears just once?

michael singh
michael singh
5,927 Points

Hey Matt,

I want the function to return all values in an array that only appear once.

1 Answer

Matt F.
Matt F.
9,518 Points
Matt F.
Matt F.
9,518 Points

Hi Michael,

Here is a function that will find all values that occur just once in an array.

function findSingles (arr) {
  return arr.reduce(function(singles, curValue, curIndex) {
    var curIndexOmittedArray = arr.slice(0, curIndex).concat(arr.slice(curIndex + 1));
    if (curIndexOmittedArray.indexOf(curValue) === -1) {
      singles.push(curValue);
    }
    return singles;
  }, []) 
}

Here is it working on CodePen: http://codepen.io/mq9_reaper/pen/grMLWa?editors=0010