Reactjs - React not updating variable state in array of deep nested objects with filter function when updating with new data

webblover
May 29, 2023
310 views
1 vote
2 Answers

I have the following code in React,

let [employee, setEmployee] = useState([])
let employeeList = [
    {
        "data": [
            {
                "name": "John",
                "email": "[email protected]",
                "status": "passed"
            },
            {
                "name": "Jane",
                "email": "[email protected]",
                "status": "failed"
            }
        ]
    }
]

When initilizing, we give as follows,

setEmployee(employeeList)

It shows both employees in table with status "passed" and "failed" in 2 rows correctly.

There is a selection box at the top which when selected with "passed",
we filter it with following function,

setEmployee(employee => employee[0].data.filter((ele, i) => ele.status === 'passed'));

I see the following filtered employee state variable,

// employee (state variable, see the original array of object of arrays is distorted here)
    [
        {
            "name": "John",
            "email": "[email protected]",
            "status": "passed"
        }
    ]

instead of,

[
    {
        "data": [
            {
                "name": "John",
                "email": "[email protected]",
                "status": "passed"
            }
        ]
    }
]

I’m new to React states and unable to achieve above format. The original employee state variable should be intact structurally but only its deep array should be filtered. I guess there is some mistake I make in line,

setEmployee(employee => employee[0].data.filter((ele, i) => ele.status === 'passed'));

Any help is very appreciated. Please don’t suggest advanced concepts like useMemo but let’s modify it slightly to achieve what I want. Thanks.

Tags: javascript-objects reactjs

Answers

- JihoonChoi
- May 26, 2023 at 3:00 pm
- 0 votes
0
Not sure that I am getting the question right, but it seems that the state you are returning when the selection box is checked, you are return the state in a different structure.

The filter function is returning an array, but with a different structure when you first initialized your state employee.

I tried it out myself, and successfully filtered the employeeList without modifying the original structure of your initial state.
```
    const handlePassed = () => {
    const newEmployeeList = employee.map((item) => {
        return {
            ...item,
            data: item.data.filter((employee) => employee.status === 'passed'),
        };
    });
    setEmployee(newEmployeeList);
};
```
I am not sure if this would be an efficient algorithm for updating your state, but I hope this is a starting point for figuring out your problem.

happy coding
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- AbdulrahmanAli
- May 26, 2023 at 3:01 pm
- 0 votes
0
You can in the setter form of the setEmployee set the original object structure.

Like so:
```
setEmployee(employee => ({data: employee[0].data.filter((ele, i) => ele.status === 'passed')}));
```
The above line basically returns the filtered result as an array value of the property data.

Other approach would be use to clone the object and set normally, like so:
```
const filteredResult = employee[0].data.filter((ele, i) => ele.status === 'passed');
const newEmployees = structuredClone(employee);
newEmployees[0].data = filteredResult;

setEmployee(newEmployees);
```
Note that I have used the structuredClone above to deep copy the old state object & to avoid any reference issues. Hope this helps. 🙂
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