as the title
console.log(arr)
console.log( obj )
as the title
console.log(arr)
console.log( obj )
for
loop, the obj
of the operation is the same object, and the obj
added in arr
is also the same object. After the for
loop, obj.id
is 4, so the obj
in arr
is all {id:4}
objects are reference types.
object is a reference type, and only the address is assigned when assigning, so the four objects in your array are all at the same address, that is, the same object
.you can modify it like this
const obj = {id: 0}
const arr = []
for (let i = 0; i < 4; iPP) {
obj.idPP
arr.push(JSON.parse(JSON.stringify(obj)))
}
console.log(arr)
in addition, don't use the markdown syntax to ask questions like this, so that others can directly copy and use your code to modify it without having to type it again
.is because of the method console.log (). If we replace it with alert (), we can get the result that meets our expectations
because arr= [. Arr,obj]
is only a shallow copy of obj, in the final analysis, it is the application of obj used. If you want to make a deep copy, you can consider changing it to this:
let obj = {id:0},arr=[]
for(let i = 0;i<4;iPP){obj.id+=1;arr=[...arr,{...obj}]}
// arr [{id:1},{id:2},{id:3},{id:4}]
of course, this is only a simple first-layer deep copy, and if obj is a more complex situation, you have to consider it separately.
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