Compare Object Ids from Array in JavaScript

Question

I got an array with some objects. Each object has an id. So when generating a new id, I want to check if an object with this id already exists. If there is an equal id, a new one should be generated.

generateId() {
    var records = store.getRecords(); // get all the objects
    var newId = getNewId(); // calculate a new id

    if (record.id == newId) // id already exists // record.id = id of the object
        newId = generateId(); // generate a new id
    else
        return newId; // return the id
}

getNewId() {
  // generate Id...
}

So how can I check all my records here if (record.id == newId) ? I use JQuery.

Do you know the strategy of generated Id? Is this a sequence? — hsd
– hsd, Commented Aug 4, 2017 at 8:35
Of which object? the record is undefined. And What should be a difference between generateId and getNewId ? — Sergej
– Sergej, Commented Aug 4, 2017 at 8:37

Adrian · Accepted Answer · 2017-08-04 08:54:42Z

2

You can use a simple for loop for simlicity, it might not be efficient if you've got a lot of records obtained. If the structure of the object is the same for all records and assuming the data type of the object value matches the newId variable, this function will serve the purpose.

function DoesExist() {
   for(var i = 0; i < records.length; i++) {
     if(records[i].id == newId)
        return true;
   }

   return false;
}

edited Aug 4, 2017 at 8:54

answered Aug 4, 2017 at 8:37

Adrian

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2 Comments

Sergej Over a year ago

Your code should be maintanable. Otherwise there should exist a variables records and newId in a parent/global scope. You should pass them as function input parameters.

Adrian Over a year ago

@Sergej, This is an example, I am not providing code that one must use. OPs code isn't formatted properly either, hence the reason for my function that I put in place.

Angelos Chalaris · Accepted Answer · 2017-08-04 08:49:43Z

The way I would go about it is to split my logic into multiple functions, so that I can check any new id against the existing ones. Then, wrapping this inside a loop, I could check generated values until one is found that is not in the array. For example (methods and values added for testing):

function generateId() {
  var records = store.getRecords(); // get all the objects
  var newId; 
  var isUnique = false; 
  while (!isUnique) { // check if unique, repeatedly
    newId = getNewId(); // calculate a new id
    isUnique = checkId(newId);
  }
  return newId; // return the id (is unique)
}
// Check if the id is unique against existing records
function checkId(newId) {
  var records = store.getRecords();
  for (var key in records)
    if (records[key].id == newId)
      return false;
  return true;
}

// Added for testing
function getNewId() {
  return Math.round(Math.random() * 10);
}
var store = {getRecords: function() {return [{id: 1}, {id: 2}, {id: 4}, {id: 6}];}}

// Actual testing
console.log(generateId());

Hitmands · Accepted Answer · 2017-08-04 09:04:22Z

1

this should work as incremental id generator:

const data = [{id: 1}, {id: 2}, {id: 3}, {id: 4}, {id: 5}, {id: 6}];

const exists = id => data.some(o => o.id === id);

const newId = (start = 0) => {
  const id = ++start;
  
  return exists(id) ? newId(id) : id;
};  


// you can also evaluate to implement some uid logic...
// there isn't much you can do on the client, but, 
// this could also help

const newUID = () => {
  const uid = Math.random().toString(32).substr(2);
  
  return exists(uid) ? newUID() : uid;
}

console.log({
  incrementalID: newId(),
  UID: newUID()
});

edited Aug 4, 2017 at 9:04

answered Aug 4, 2017 at 8:46

Hitmands

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7 Comments

Question3r Over a year ago

so id => data.some(o => o.id === id) should be the important part

Hitmands Over a year ago

also, a recursive approach is the best for this case.

Question3r Over a year ago

so for my case it should be if (newId => records.some(record => record.id === newId)) right? I get a call stack exception but I think I made an mistake somewhere else

Hitmands Over a year ago

your call stack exception could depend on maximum call stack hit, you might end up on an infinite loop...

Question3r Over a year ago

It's a maximum callstack exception but I don't get the reason

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