JSON.stringify()

The JSON.stringify() static method in JavaScript is used to convert a JavaScript object or value into a JSON string. It can optionally include a replacer function or array and control formatting with a space parameter.

Syntax

</>
Copy
JSON.stringify(value)
JSON.stringify(value, replacer)
JSON.stringify(value, replacer, space)

Parameters

ParameterDescription
valueThe value to convert to a JSON string. It can be an object, array, string, number, or boolean.
replacer (optional)A function or array that alters the behavior of the stringification process. If omitted, all properties of the object are included.
space (optional)A string or number used for pretty-printing the JSON output. Numbers indicate the number of spaces; strings are directly used for indentation.

Return Value

The JSON.stringify() method returns a string representing the JSON-formatted version of the given value.

Examples

1. Converting an Object to JSON

In this example, an object is converted to a JSON string using JSON.stringify().

</>
Copy
const user = { name: "Arjun", age: 25, city: "New York" };

const jsonString = JSON.stringify(user);
console.log(jsonString);

Output

{"name":"Arjun","age":25,"city":"New York"}
  1. The JSON.stringify() method converts the user object to a JSON string.

2. Using a Replacer Function

The replacer function can be used to filter or transform properties during stringification.

</>
Copy
const user = { name: "Arjun", age: 25, city: "New York" };

const jsonString = JSON.stringify(user, (key, value) => {
  if (key === "age") {
    return undefined; // Exclude the "age" property
  }
  return value;
});
console.log(jsonString);

Output

{"name":"Arjun","city":"New York"}
  1. The replacer function excludes the age property from the final JSON string.

3. Using an Array as Replacer

An array replacer allows you to specify which properties should be included in the JSON string.

</>
Copy
const user = { name: "Arjun", age: 25, city: "New York" };

const jsonString = JSON.stringify(user, ["name", "city"]);
console.log(jsonString);

Output

{"name":"Arjun","city":"New York"}
  1. Only the name and city properties are included in the JSON string.

4. Pretty-Printing JSON

The space parameter is used to format the JSON output with indentation for better readability.

</>
Copy
const user = { name: "Arjun", age: 25, city: "New York" };

const jsonString = JSON.stringify(user, null, 2);
console.log(jsonString);

Output

{
  "name": "Arjun",
  "age": 25,
  "city": "New York"
}
  1. The space parameter formats the JSON string with a 2-space indentation.

5. Handling Circular References

Using JSON.stringify() with circular references will throw an error. You can handle this with a replacer function.

</>
Copy
const obj = {};
obj.self = obj;

const jsonString = JSON.stringify(obj, (key, value) => {
  if (value === obj) {
    return "[Circular]";
  }
  return value;
});
console.log(jsonString);

Output

"[Circular]"
  1. The replacer function detects circular references and replaces them with a placeholder.