What Does JSON.stringify() Do?

JSON.stringify() converts a JavaScript object or value into a JSON-formatted string.

Syntax:

JSON.stringify(value, replacer, space)

• value - The object or value to convert into a JSON string.
• replacer (optional) - A function or array that filters properties before converting.
• space (optional) - A number or string to format the JSON output for readability.

Example Usage

Basic Example

const obj = { name: "John", age: 30 };
const jsonString = JSON.stringify(obj);
console.log(jsonString); 
// Output: '{"name":"John","age":30}'
    

With Arrays

const arr = [1, 2, 3];
console.log(JSON.stringify(arr));
// Output: "[1,2,3]"
    

With Null Values

const obj = { name: "Alice", age: null };
console.log(JSON.stringify(obj));
// Output: '{"name":"Alice","age":null}'
    

Why Use JSON.stringify()?

• To Send Data in HTTP Requests: Required when sending data via fetch() in JSON format.
• To Store Data Locally: Used to store objects in localStorage or sessionStorage.
• For Debugging: Helps convert objects into readable strings for logging.

Example: Sending Data in a Fetch Request

fetch("https://jsonplaceholder.typicode.com/posts", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({
        title: "My Post",
        body: "This is the content.",
        userId: 1
    })
})
.then(response => response.json())
.then(data => console.log(data));