要將JSON字符串解析為JavaScript對(duì)象，應(yīng)使用JSON.parse()方法，它能將有效的JSON字符串轉(zhuǎn)換為對(duì)應(yīng)的JavaScript對(duì)象，支持嵌套對(duì)象和數(shù)組的解析，但對(duì)無(wú)效JSON會(huì)拋出錯(cuò)誤，因此需用try...catch處理異常，同時(shí)可通過第二個(gè)參數(shù)的reviver函數(shù)在解析時(shí)轉(zhuǎn)換值，如將日期字符串轉(zhuǎn)為Date對(duì)象，從而實(shí)現(xiàn)安全可靠的數(shù)據(jù)轉(zhuǎn)換。

To parse a JSON string into a JavaScript object, use the built-in JSON.parse() method. This method takes a valid JSON string and converts it into a corresponding JavaScript object.

Using JSON.parse()

The most common and reliable way to parse JSON is with JSON.parse() . Here's how it works:

 const jsonString = '{"name": "John", "age": 30, "city": "New York"}';
const obj = JSON.parse(jsonString);

console.log(obj.name); // Output: John
console.log(obj.age); // Output: 30

This works for nested objects and arrays too:

 const jsonArrayString = '[{"id": 1, "title": "Learn JS"}, {"id": 2, "title": "Build App"}]';
const posts = JSON.parse(jsonArrayString);

console.log(posts[0].title); // Output: Learn JS

Handling Errors

Since JSON.parse() throws an error if the string is not valid JSON, wrap it in a try...catch block when dealing with untrusted or uncertain input:

 const badJson = "{ name: 'John' }"; // Invalid JSON (missing quotes)

try {
  const obj = JSON.parse(badJson);
  console.log(obj);
} catch (err) {
  console.error("Invalid JSON string:", err.message);
}

Common reasons for parsing errors include:

• Missing or mismatched quotes
• Trailing commas
• Single quotes instead of double quotes
• Comments in the JSON (not allowed)

Parsing with a Reviver Function

JSON.parse() also accepts a second parameter called a reviver function , which lets you transform the parsed values before returning them:

 const jsonString = '{"name": "Alice", "age": "25", "joined": "2023-01-15T00:00:00Z"}';

const obj = JSON.parse(jsonString, (key, value) => {
  if (key === 'joined') {
    return new Date(value); // Convert date string to Date object
  }
  return value;
});

console.log(obj.joined instanceof Date); // true

This is useful for automatically converting dates, filtering keys, or sanitizing data during parsing.

Basically, JSON.parse() is the standard and safe way to turn a JSON string into a usable JavaScript object — just make sure the input is valid JSON and handle possible errors appropriately.

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