How to update a single key value pair in an array of objects in react? Code Answer

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I am trying to update a single key value pair in an array of objets using React.

Here is the setup

An array of objects

const array = [
  {id:1,name:'Tyler',age:23},
  {id:2,name:'Lauren',age:28},
  {id:3,name:'Nico',age:14},
]

Given an id and age, I want to be able to update the single object that matches the id. For example, given an id of 2 and age of 56, {id:2,name:'Lauren',age:28} should change to {id:2,name:'Lauren',age:56}

My approach

I’ve set up useState to copy the array of object. However, I am struggling to filter out for the selected id, change the age, and return the updated array.

This is what I currently have:

import { useState } from "react";

const array = [
  { id: 1, name: "Tyler", age: 23 },
  { id: 2, name: "Lauren", age: 28 },
  { id: 3, name: "Nico", age: 14 }
];

export default function App() {
  const [list, setList] = useState(array);

  const updateAge = (id = 2, age = 56) => {
    setList([...list, list.filter((item) => item.id === id)]);
  };

  return (
    <>
      <ul>
        {list.map((item) => {
          return (
            <li>
              {item.name} | {item.age}
            </li>
          );
        })}
      </ul>
      <button onClick={updateAge}>Update age</button>
    </>
  );
}

Here is my codesandbox link

Answer

You can use the map function to produce a new array to set the state with.

const updateAge = (id, age) => {
    console.log(id, age);
    setList(
      list.map((item) => {
        if (item.id === id) {
          return { ...item, age };
        } else {
          return item;
        }
      })
    );
  };

If the id matches, it will merge the new age, otherwise it will return the item unchanged.

Note that it will only produce new objects for updated age, the rest will be the same references. That is to say it will be a new array, but most objects (except the changed one) will be the same. If you want new objects you can return { ...item } in the else clause as well.

In this particular case React will only be concerned that you set the state with new array.

Here’s the sandbox

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