Remove an Element from state Array in React

Remove an element from state Array in React #

To remove an element from a state array in React:

Use the filter() method to iterate over the array.
On each iteration, check if a condition is met.
Set the state to the new array that the filter method returned.

App.js

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import {useState} from 'react';

export default function App() {
  // 👇️ primitives array
  const [names, setNames] = useState(['Alice', 'Bob']);

  const removePrimitiveFromArray = () => {
    // ✅ remove 'Bob' from array
    setNames(current =>
      current.filter(element => {
        return element !== 'Bob';
      }),
    );
  };

  const initialState = [
    {id: 1, name: 'Alice', country: 'Austria'},
    {id: 2, name: 'Bob', country: 'Belgium'},
  ];

  // 👇️ array of objects
  const [employees, setEmployees] = useState(initialState);

  const removeObjectFromArray = () => {
    // ✅ Remove object with id 2 from array
    setEmployees(current =>
      current.filter(obj => {
        return obj.id !== 2;
      }),
    );
  };

  return (
    <div>
      <button onClick={removePrimitiveFromArray}>
        Remove string from state array
      </button>

      {names.map((element, index) => {
        return <h2 key={index}>{element}</h2>;
      })}

      <hr />
      <br />

      <button onClick={removeObjectFromArray}>
        Remove object from state array
      </button>

      {employees.map(employee => {
        return (
          <div key={employee.id}>
            <h2>name: {employee.name}</h2>
            <h2>country: {employee.country}</h2>

            <hr />
          </div>
        );
      })}
    </div>
  );
}

The code snippet shows how to remove a primitive (a string) and an object from a state array.

We initialized an array of names and an array of employees with 2 calls to the useState hook.

The function we passed to the Array.filter method will get called with each element in the array.

App.js

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const names = ['Alice', 'Bob'];

const result = names.filter(element => {
  return element !== 'Bob';
});

// 👇️ ['Alice']
console.log(result);

// ---------------------------------------------

const employees = [
  {id: 1, name: 'Alice', country: 'Austria'},
  {id: 2, name: 'Bob', country: 'Belgium'},
];

const result2 = employees.filter(obj => {
  return obj.id !== 2;
});

// 👇️ [{id: 1, name: 'Alice', country: 'Austria'}]
console.log(result2);

The filter method returns a new array containing only the elements for which the callback function returned a truthy value.

If the condition is never met, the Array.filter function returns an empty array.

The first example returns a truthy value for all elements that are not equal to the string Bob, and the second returns a truthy value for all objects that don't have an id property equal to 2.

We passed a function to setState, because the function is guaranteed to be invoked with the current (most up to date) state.

App.js

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setNames(current =>
  current.filter(element => {
    return element !== 'Bob';
  }),
);

setEmployees(current =>
  current.filter(obj => {
    return obj.id !== 2;
  }),
);

When the next state is computed using the previous state, pass a function to setState.

Otherwise, we might get some weird race condition if the state array we have access to does not represent the most up to date value.

If you need to remove an element from a state array based on multiple conditions, use the logical AND (&&) or logical OR (||) operators.

App.js

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const initialState = [
  {id: 1, name: 'Alice', country: 'Austria'},
  {id: 2, name: 'Bob', country: 'Belgium'},
  {id: 3, name: 'Carl', country: 'Austria'},
];

const [employees, setEmployees] = useState(initialState);

const remove = () => {
  setEmployees(current =>
    current.filter(employee => {
      return employee.id !== 3 && employee.id !== 2;
    }),
  );
};

We used the logical AND (&&) operator which will only return a truthy value if both conditions are met.

The callback function returns true only if the id property of the object is not equal to 3 and not equal to 2.

And here is an example that uses the logical OR (||) operator.

App.js

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const initialState = [
  {id: 1, name: 'Alice', country: 'Austria'},
  {id: 2, name: 'Bob', country: 'Belgium'},
  {id: 3, name: 'Carl', country: 'Austria'},
];

const [employees, setEmployees] = useState(initialState);

const remove = () => {
  setEmployees(current =>
    current.filter(employee => {
      return employee.name === 'Alice' || employee.name === 'Carl';
    }),
  );
};

Either of the 2 conditions has to evaluate to a truthy value for the element to be added to the new array.

In other words, if the name property on the object is equal to Alice or equal to Carl, the object will be added to the new array. All other objects are filtered out from the array.

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Remove an Element from state Array in React

Remove an element from state Array in React #

Borislav Hadzhiev