数组中所有对象的 1 个对象的值变化

Question

I have an array of objects. Each object has a key quantity and value . I want to duplicate each object in the array based on its quantity. Next, I want to manipulate only one of the duplicated object in the array. But on manipulating value of 1 object, value of all duplicated objects change. Here is my code:

let arr = [
    { id: 1, quantity: 3, value: 10 },
    { id: 2, quantity: 1, value: 5 },
    { id: 2, quantity: 5, value: 5 },
  ];
  const newArr = [];
  for (const a of arr) {
    if (a.quantity > 1) {
      let quantity = a.quantity;
      a.quantity = 1;
      while (quantity--) {
        newArr.push(a);
      }
    }
  }
  arr = newArr;
  arr[0].value = 1;

When I changed the value of arr[0] to 1 , value field of arr[1] and arr[2] also changed to 1.

I have tried copying the object using spread operator and JSON.parse(JSON.parse()) , but none has worked.

Answer 1

Because newArr.push(a) . a push to newArr ref to element of arr

You can edit same as :

 let arr = [ { id: 1, quantity: 3, value: 10 }, { id: 2, quantity: 1, value: 5 }, { id: 2, quantity: 5, value: 5 }, ] const newArr = [] for (const a of arr) { if (a.quantity > 1) { let quantity = a.quantity; a.quantity = 1; while (quantity--) { newArr.push({...a}) } } } arr = [...newArr] arr[0].value = 1 console.log(arr) // example for Memory Management let a = { id: 1, quantity: 3, value: 10 } let b = { id: 1, quantity: 3, value: 10 } let c = arr[0] let d = {...arr[0]} console.log(a === arr[0]) // false : different allocates memory for contain value console.log(a === b) // false : different allocates memory for contain value console.log(c === arr[0]) // true : refer to a memory console.log(d === arr[0]) // false : different allocates memory for contain value