JavaScript

The JSON.parse() method in JavaScript is used to convert a JSON string into a JavaScript object.

✅ In simple words:
JSON string → JavaScript object

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📦 Syntax

JSON.parse(text[, reviver]);

Parameters:

• text: A valid JSON string to be parsed.
• reviver (optional): A function that allows transformation of the result before returning.

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✅ Example 1: Basic Usage

const jsonStr = '{"name": "Alice", "age": 25}';

const user = JSON.parse(jsonStr);

console.log(user.name); // Output: Alice
console.log(user.age);  // Output: 25

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✅ Example 2: Parsing Arrays

const jsonArray = '["HTML", "CSS", "JavaScript"]';

const skills = JSON.parse(jsonArray);

console.log(skills[1]); // Output: CSS

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❗ Invalid JSON will cause an Error

const badJson = "{name: 'John'}"; // ❌ Invalid JSON

try {
  const obj = JSON.parse(badJson);
} catch (error) {
  console.error("Error parsing JSON:", error.message);
}

🔧 Fix:

Always wrap keys and strings in double quotes:

const goodJson = '{"name": "John"}';

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🧠 Optional: Using the Reviver Function

The reviver function allows you to modify values during parsing.

const jsonStr = '{"name": "John", "age": "30"}';

const person = JSON.parse(jsonStr, (key, value) => {
  if (key === "age") {
    return Number(value); // Convert age to number
  }
  return value;
});

console.log(person.age); // Output: 30 (number)

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✅ Summary

Feature	Description
Purpose	Converts JSON string → JavaScript object
Input	Must be a valid JSON string
Common Use Case	Reading data from APIs or localStorage
Optional reviver	Custom processing while parsing

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