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How to update key with new value in javascript

In JavaScript, you can update the value of an existing key in an object by simply assigning a new value to that key. Let’s know how to update¬†object¬†value¬†by¬†key in¬†array in javascript.

For example, let’s say you have an object called person with a name key and you want to update the value of name to "John":

let person = { name: "Jane", age: 30 };
person.name = "John";
console.log(person); // Output: { name: "John", age: 30 }

In this example, we assigned the new value "John" to the name key of the person object, effectively updating the value of the name key.

javascript update object value by key

You can also update the value of a key using the [] notation. For example, if you have a variable key that contains the name of the key you want to update, you can use it like this:

let person = { name: "Jane", age: 30 };
let key = "name";
person[key] = "John";
console.log(person); // Output: { name: "John", age: 30 }

In this example, we used the [] the notation to update the value of the name key using the value of the key variable.

It’s important to note that if you try to update the value of a key that doesn’t exist in the object, JavaScript will create a new key with the specified value. For example:

let person = { name: "Jane", age: 30 };
person.city = "New York";
console.log(person); // Output: { name: "Jane", age: 30, city: "New York" }

In this example, we assigned the value "New York" to the non-existent city key of the person object, effectively creating a new key with the specified value.

How to update the object with another object using Object.assign() in javascript

To Update the object with another object, Object.assign() can be used.

const books={
name:"Hindi",
category:"Art"
}
const books1={
name:"Physics",
category:"science"
}

books.assign(books1)

How to add or merge objects in javascript

To merge or add js objects you can use the spread operator in which one or more js objects are appended to another object

const books1={name:"hindi"}
const books2={name:"english"}
const allBooks={...books1,...books2}
allbooks={
name:"hindi",
name:"english"
}

In summary, you can update the value of an existing key in a JavaScript object by simply assigning a new value to that key, or by using the [] notation. If the key doesn’t exist, JavaScript will create a new key with the specified value.

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