js里面stringify

let obj = {
  name: "Alice",
  age: 25,
  skills: ["JavaScript", "Python"]
};

let jsonString = JSON.stringify(obj);
console.log(jsonString); // 输出: {"name":"Alice","age":25,"skills":["JavaScript","Python"]}

// 使用 replacer 函数
let replacer = (key, value) => {
  if (typeof value === "string") {
    return value.toUpperCase();
  }
  return value;
};

let jsonStringWithReplacer = JSON.stringify(obj, replacer);
console.log(jsonStringWithReplacer); // 输出: {"name":"ALICE","age":25,"skills":["JAVASCRIPT","PYTHON"]}

// 使用 space 参数美化输出
let prettyJsonString = JSON.stringify(obj, null, 2);
console.log(prettyJsonString);
/*
输出:
{
  "name": "Alice",
  "age": 25,
  "skills": [
    "JavaScript",
    "Python"
  ]
}
*/

let circularReference = {};
circularReference.myself = circularReference;

let seen = new WeakSet();
let jsonStringCircular = JSON.stringify(circularReference, (key, value) => {
  if (typeof value === "object" && value !== null) {
    if (seen.has(value)) {
      return '[Circular]';
    }
    seen.add(value);
  }
  return value;
});
console.log(jsonStringCircular); // 输出: {"myself":"[Circular]"}