Here is the code i have:
let testp = {
value: ''
}
let data = [];
for (let i = 0; i < 5; i++) {
testp.value = i;
data.push(testp);
}
console.log(data)
The data return is:
[ { value: 4 },
{ value: 4 },
{ value: 4 },
{ value: 4 },
{ value: 4 } ]
why? I think the result is like this:
[ { value: 0 },
{ value: 1 },
{ value: 2 },
{ value: 3 },
{ value: 4 } ]
You're pushing a reference to the object testp into the array 5 times, editing the value of value each time.
Here's another example:
let foo = { 'a': 1 };
let bar = [foo, foo, foo];
foo.a = 2;
console.log(foo[2]);
// 2
The array bar contains three references to foo. Changing the content of the object will change the content of the object everywhere it is referenced.
If you want new objects you have to create them somewhere. For example:
// Function that constructs the new objects
let foo = (value) => { return { "value": value } };
let data = [];
for (let i = 0; i < 5; i++) {
data.push(foo(i));
}
Assigning testp.value inside the loop was causing the problem.Instead you could do
let testp = {
value: ''
}
let data = [];
for (let i = 0; i < 5; i++) {
data.push({
value: i
});
}
console.log(data)
testpis a reference to the javascript object; when you calldata.push(testp), you're merely adding to the array another reference to that same object. not a copy of the current state of the object4for every value, because JavaScript passes objects by reference, not by value. Thus you're modifying the same object on every iteration of the loop, not a different object.