Remove duplicates and replace from an array

Question

I have an array of elements:

arr = ["one", "two", "three", "one", "two", "one"]

I want to replace duplicates with empty strings in array:

output= ["", "", "three", "", "", ""]

Here is my code:

let obj = {}

for(let i=0; i<arr.length; i++) {
   let a = arr[i];
   if(obj[a]) obj[a]+=1
   else obj[a]=1
}

let output = []

for(let i=0; i<arr.length; i++) {
   output[i] = obj[arr[i]] > 1 ? "" : arr[i];
}

Is this a better approach or is there a way to improve the performance?

If this code works, and you are simply asking if there is a better approach, then this question is off topic for StackOverflow. If this is the case it would be more appropriate on codereview — Taplar
– Taplar, Commented Jul 30, 2020 at 21:53

Unmitigated · Accepted Answer · 2020-07-30 21:54:29Z

1

You can simplify your code using reduce and map, but there aren't really any optimizations that could be made.

let arr = ["one", "two", "three", "one", "two", "one"];
let freq = arr.reduce((acc,curr)=>(acc[curr] = (acc[curr] || 0) + 1, acc), {});
let res = arr.map(x=>freq[x] === 1 ? x: '');
console.log(res);

answered Jul 30, 2020 at 21:54

Unmitigated

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Comments

Sven.hig · Accepted Answer · 2020-07-30 22:24:22Z

0

In your ternary operator you forgot to assign the output array to expected value so it should be

 output[i] = objx[arr[i]] > 1 ? output[i]="" : output[i]=arr[i]

arr = ["one", "two", "three", "one", "two", "one"]


 obj = {}

for(let i=0; i<arr.length; i++) {
   let a = arr[i];
   if(obj[a]) obj[a]+=1
   else obj[a]=1
}
let output = []

for(let i=0; i<arr.length; i++) {
   output[i] = obj[arr[i]] > 1 ? output[i]="" : output[i]=arr[i]
}

console.log(output)

Here is a different simpler approach using foreach and map

arr = ["one", "two", "three", "one", "two", "one"]

 var obj = {}  ;
arr.forEach(e => {
  obj[e] = obj[e] || 0
  obj[e] =  obj[e] + 1
})
res= arr.map(x => obj[x] > 1 ? "" : x)
console.log(res)

edited Jul 30, 2020 at 22:24

answered Jul 30, 2020 at 21:58

Sven.hig

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2 Comments

Sven.hig Over a year ago

downvoter please feel free to comment why my answer is incorrect, I would like to learn from my mistakes :) thanks

Unmitigated Over a year ago

Looking back at this, the downvote was likely because output[i] = objx[arr[i]] > 1 ? output[i]="" : output[i]=arr[i] is redundant. The original code in the question was already correct.

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