Compare key values within object for duplicate updated

Question

This is a follow up post from Compare key values within object for duplicate for a follow up answer.

I have an object:

myObj = {
  attendent-0-id:"123",
  attendent-0-name:"Bob Smith",
  attendent-1-id:"1234",
  attendent-1-name:"Alex Smith",
  attendent-2-id:"123",
  attendent-2-name:"Charlie Smith",
  attendent-0-id:"123",
  attendent-0-name:"John Smith",
  attendent-maxGuest:1,
  attendent-party-name:"",
}

Thanks to help on here (Rick) I was able to get 90% of the way there.

function errorOnDuplicateIds(obj) {
  const map = {};
  const pattern = /^attendent-\d+-id$/;

  for (const key of Object.keys(obj)) {
    if (pattern.test(key)) {      
      const value = obj[key]

      if (value in map) {
        map[value] = [map[value], key];       
      } else {
        map[value] = key
      }
    }    
  }
return map;
}

I am getting a return of:

array:[
  0:(2) ["attendent-0-name", "attendent-1-name"]
  1:"attendent-2-name"
]

but I am looking for:

array:[
  0:(2) ["attendent-0-name", "attendent-1-name", "attendent-2-name"]
]

The issue I am having is that while this works if there are two matching keys it will not work (Correctly) if there are three or more.

I believe you should have edited your original question, not create another one. — Edmundo Santos
– Edmundo Santos, Commented Aug 1, 2018 at 15:13
Sounds like you shouldn't have accepted an answer that doesn't work? — Bergi
– Bergi, Commented Aug 1, 2018 at 15:13
It did work for what I needed but things have changed. The person who provided said answer asked for a new question to keep things separate. — Ryley Ameden
– Ryley Ameden, Commented Aug 1, 2018 at 15:19
It would help to know why it is not working Correctly. What are the expected results when there are three or more of the same id and what is actually given? — hajile78
– hajile78, Commented Aug 1, 2018 at 15:22
What is the desired behavior when there is more than one match? — Mark
– Mark, Commented Aug 1, 2018 at 15:22

Mark · Accepted Answer · 2018-08-01 16:00:11Z

2

If you want to have an array of all matches for each key in you map, you need to start by setting an array when you find a key the first time. On subsequent matches, just push into that array:

const myObj = {'attendent-0-id': "1234",'attendent-0-name': "Bob Smith",'attendent-1-id': "123",'attendent-1-name': "Alex Smith",'attendent-2-id': "123",'attendent-2-name': "Charlie Smith",'attendent-maxGuest': 1,'attendent-party-name': "",};
  
function errorOnDuplicateIds(obj) {
  const map = {};
  const pattern = /^attendent-\d+-id$/;

  for (const key of Object.keys(obj)) {
    if (pattern.test(key)) {
      const value = obj[key]

      if (value in map) {
        map[value].push(key); // push a new value 
      } else {
        map[value] = [key] // set it to an array
      }
    }
  }

  /* if you only want lengths > 1
     otherwise just return map   */
  let filtered = Object.entries(map)
    .reduce((a, [key, value]) =>  value.length > 1 ? Object.assign(a, {[key]: value}) : a, {})

  return filtered;
}

console.log(errorOnDuplicateIds(myObj));

If you are only interested in values with more than one hit, you can reduce() down to a map with only values of length greater than one, which is what the last bit in the snippet does.

edited Aug 1, 2018 at 16:00

answered Aug 1, 2018 at 15:33

Mark

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3 Comments

Mark Over a year ago

Great @RyleyAmeden, note that this will return all values even those with only one ID. I added an edit that shows a quick way to filter to only dupes.

Ryley Ameden Over a year ago

I noticed that, thank you! It is giving me an error that .length doesn't exists on {}

Mark Over a year ago

@RyleyAmeden maybe your passing in the wrong thing, not sure. I added it to the snippet so you can see it in action.

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