Question 287099 in Javascript Question posted in
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Javascript – How to reset array of object duplicate value set empty value

How to set the duplicate value is an array object to empty string.

const arr= [
{ name: 'someName1', age: 12 },
{ name: 'someName2', age: 13 },
{ name: 'someName3', age: 14 },
{ name: 'someName4', age: 15 }, 
{ name: 'someName4', age: 16 }, 
{ name: 'someName5', age: 15 },
{ name: 'someName3', age: 17 }, 
{ name: 'someName2', age: 18 },
];

expected result like below:

const resultArr = [
  { name: 'someName1', age: 12 },
  { name: 'someName2', age: 13 },
  { name: 'someName3', age: 14 },
  { name: 'someName4', age: 15 }, 
  { name: '', age: 16 },
  { name: 'someName5', age: 15 },  
  { name: '', age: 17 }, 
  { name: '', age: 18 },
]

I have tried but not getting exact result,

arr.map((res, i=index) => {
      const getNum = i === 0 ? i : i - 1;
      const prev = arr[getNum].name;

      if (res.name === prev) {
          res.name = '';
      }
Tags:

3

Answers


  1. 0

    Your function is incorrect. It only compares the current value with the previous one, and always clears the name at index 0.

    A more effective approach would be to initialize an array of strings before the map function, and update this array whenever a new name is encountered. Then, simply check if the current name already exists in the array.

    const existingNames = [];
arr.map((res) => {
  if(existingNames.includes(res.name)) {
    res.name = '';
  } else {
    existingNames.push(res.name)
  }
  return res;
});
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  2. 0

    You could take a Set in a closure for seen names and map either the object or take a new object with empty name property.

    const 
    data = [{ name: 'someName1', age: 12 }, { name: 'someName2', age: 13 }, { name: 'someName3', age: 14 }, { name: 'someName4', age: 15 },  { name: 'someName4', age: 16 },  { name: 'someName5', age: 15 }, { name: 'someName3', age: 17 },  { name: 'someName2', age: 18 }],
    result = data.map((seen => o => seen.has(o.name) || !seen.add(o.name)
        ? { ...o, name: '' }
        : o
    )(new Set));

console.log(result);
    .as-console-wrapper { max-height: 100% !important; top: 0; }
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  3. 0

    You can keep track of the names you’ve seen with a Set while you’re mapping over the data to create the new data.

    const arr = [
  { name: "someName1", age: 12 },
  { name: "someName2", age: 13 },
  { name: "someName3", age: 14 },
  { name: "someName4", age: 15 },
  { name: "someName4", age: 16 },
  { name: "someName5", age: 15 },
  { name: "someName3", age: 17 },
  { name: "someName2", age: 18 },
];

const seenNames = new Set();

const newArr = arr.map((el) => {
  if(seenNames.has(el.name)) {
    // If we've seen the name already, replace it with an empty string.
    return {...el, name: ''};
  }
  // Record the name, and return the element as-is.
  seenNames.add(el.name);
  return el;
});

console.log(newArr);
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