How to handle duplicate IDs in JavaScript array objects and assign different values?

Cleverly solve the problem of duplicate ID in JavaScript array objects

This article provides an efficient JavaScript method for processing duplicate IDs in array objects and assigning different values ​​to objects with the same ID.

Suppose we have an array object containing duplicate IDs:

 const list = [
  { id: 1, name: 'Xiao Ming' },
  { id: 1, name: 'Xiaohong' },
  { id: 2, name: 'Xiaoqiang' },
  { id: 3, name: 'Xiao Zhang' },
  { id: 4, name: 'Xiaolan' },
  { id: 1, name: 'Xiaoqing' },
  { id: 4, name: 'Xiaoqing' }
];

Our goal is to add a value attribute to each object with a duplicate ID and give it a different boolean value (true or false). The final result should be as follows:

 const list = [
  { id: 1, name: 'Xiao Ming', value: true },
  { id: 1, name: 'Xiaohong', value: false },
  { id: 2, name: 'Xiaoqiang' },
  { id: 3, name: 'Xiao Zhang' },
  { id: 4, name: 'Xiaolan', value: true },
  { id: 1, name: 'Xiaoqing', value: true },
  { id: 4, name: 'Xiaoqing', value: false }
];

To achieve this, we can use one object to track the number of occurrences of the ID and use another object to record the value that each ID has been assigned.

The following is the implementation code:

 const list = [
  { id: 1, name: 'Xiao Ming' },
  { id: 1, name: 'Xiaohong' },
  { id: 2, name: 'Xiaoqiang' },
  { id: 3, name: 'Xiao Zhang' },
  { id: 4, name: 'Xiaolan' },
  { id: 1, name: 'Xiaoqing' },
  { id: 4, name: 'Xiaoqing' }
];

const idCounts = {};
const idValues ​​= {};

list.forEach(item => {
  idCounts[item.id] = (idCounts[item.id] || 0) 1;
});

list.forEach(item => {
  if (idCounts[item.id] > 1) {
    if (!idValues[item.id]) {
      idValues[item.id] = true;
    }
    item.value = idValues[item.id];
    idValues[item.id] = !idValues[item.id];
  }
});

console.log(list);

This code first counts the number of times each ID appears, then iterates over the array, adds value attributes to objects with repeated IDs, and alternately assigns true and false values. The idValues ​​object ensures that subsequent objects with the same ID will get different boolean values. This method is simple and efficient, easy to understand and maintain.

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