JSON.parse() and JSON.stringify(): The JavaScript Developer's Guide

JSON.parse() andJSON.stringify()are in almost every JavaScript application — from reading API responses to storing data in localStorage. Here's everything you need to know to use them correctly.

JSON.parse() — Converting JSON String to Object

const obj = JSON.parse('{"name":"Alice","age":30}');
// obj.name → "Alice"

// Always wrap in try/catch — invalid JSON throws SyntaxError
try {
  const data = JSON.parse(response);
} catch (e) {
  console.error("Invalid JSON:", e.message);
}

JSON.stringify() — Converting Object to JSON String

const json = JSON.stringify({ name: "Alice", age: 30 });
// → '{"name":"Alice","age":30}'

// Pretty-print with indent
JSON.stringify(obj, null, 2);

// Custom replacer to filter keys
JSON.stringify(obj, ["name"]); // only include "name"

The Reviver Function

// Convert date strings back to Date objects
JSON.parse(json, (key, value) =>
  key === "date" ? new Date(value) : value
);

Deep Cloning With JSON

// Simple deep clone (loses functions, undefined, symbols)
const clone = JSON.parse(JSON.stringify(obj));

// Modern alternative (structuredClone, supported 2022+)
const clone = structuredClone(obj);

What JSON Can't Represent

• undefined values are omitted
• Functions are omitted
• Infinity and NaN become null
• Circular references throw a TypeError