JS JSON

What Is JSON?

JSON is a text format used to store and exchange data. Its simple, language-independent syntax made JSON the standard format for web APIs, configuration files, and data sent between a server and a browser.

उदाहरण: What Is JSON?

const data = { name: "Sam", age: 30 };
const jsonString = JSON.stringify(data);
console.log(jsonString); // used to exchange data with APIs

JSON.parse()

JSON.parse() converts a JSON string into a JavaScript value. If the string isn't valid JSON, JSON.parse() throws a SyntaxError, so parsing untrusted input should generally be wrapped in a try/catch.

उदाहरण: JSON.parse()

// Declare the constant `jsonString`, set to '{"name": "Sam", "age": 30}'
// Declare the constant `jsonString`, set to '{"name": "Sam", "age": 30}'
const jsonString = '{"name": "Sam", "age": 30}';
// Declare the constant `obj`, set to `JSON.parse(jsonString)`
// Declare the constant `obj`, set to `JSON.parse(jsonString)`
const obj = JSON.parse(jsonString);
// Print `obj.name` to the console
// Print `obj.name` to the console
console.log(obj.name);

JSON.stringify()

JSON.stringify() converts a JavaScript value into a JSON string.

Functions, undefined values, and symbols are silently dropped by JSON.stringify(), since JSON has no way to represent them — worth knowing before you rely on a round-trip being lossless.

उदाहरण: JSON.stringify()

const data = { name: "Sam", greet: function () {}, id: undefined };
console.log(JSON.stringify(data)); // functions/undefined dropped

JSON Data Types

JSON supports strings, numbers, booleans, null, objects, and arrays.

Because JSON has no concept of dates or functions, those need to be converted to plain values (like an ISO date string) before stringifying, and converted back manually after parsing.

उदाहरण: JSON Data Types

console.log(JSON.stringify({ a: 1, b: "text", c: true, d: null, e: [1, 2] }));

Practical JSON

JSON is commonly used with APIs, configuration files, and saved application data.

A typical fetch() call parses a JSON response body with response.json(), and a typical POST request stringifies a JavaScript object before sending it in the request body.

उदाहरण: Practical JSON

const payload = JSON.stringify({ name: "Sam" });
console.log(payload); // typical POST body
const response = JSON.parse(payload);
console.log(response.name); // typical parsed API response