如何将替换功能与JSON Stringify一起使用? [英] How Do I Use The Replacer Function With JSON Stringify?

问题描述

我一直在尝试使用

const fs = require("fs");
const settings = require("./serversettings.json")
let reason = args.join(' ');
function replacer(key, value) {
    return reason;
}
fs.writeFileSync(settings, JSON.stringify(settings.logchannel, replacer))

在我看来，这是行不通的，所以我试图弄清楚替代品是如何工作的，因为MDN使我更加困惑.

It seems like to me that it doesn't work, so I'm trying to figure out how replacers work as MDN made me even more confused.

推荐答案

replacer函数需要一个键和一个值(当它通过对象及其子对象时)，并期望返回一个新值(字符串类型) )，它将替换原始值.如果返回undefined，则在结果字符串中将省略整个键/值对.

The replacer function takes a key and a value (as it passes through the object and its sub objects) and is expected to return a new value (of type string) that will replace the original value. If undefined is returned then the whole key-value pair is omitted in the resulting string.

示例:

1. 记录传递给replacer函数的所有键值对:

var obj = {
  "a": "textA",
  "sub": {
    "b": "textB"
  }
};

var logNum = 1;
function replacer(key, value) {
  console.log("--------------------------");
  console.log("Log number: #" + logNum++);
  console.log("Key: " + key);
  console.log("Value:", value);
  
  return value;                    // return the value as it is so we won't interupt JSON.stringify
}

JSON.stringify(obj, replacer);

1. 将字符串" - altered"添加到所有字符串值:

1. Add the string " - altered" to all string values:

var obj = {
  "a": "textA",
  "sub": {
    "b": "textB"
  }
};

function replacer(key, value) {
  if(typeof value === "string")    // if the value of type string
    return value + " - altered";   // then append " - altered" to it
  return value;                    // otherwise leave it as it is
}

console.log(JSON.stringify(obj, replacer, 4));

1. 忽略所有数字类型的值:

var obj = {
  "a": "textA",
  "age": 15,
  "sub": {
    "b": "textB",
    "age": 25
  }
};

function replacer(key, value) {
  if(typeof value === "number")    // if the type of this value is number
    return undefined;              // then return undefined so JSON.stringify will omitt it 
  return value;                    // otherwise return the value as it is
}

console.log(JSON.stringify(obj, replacer, 4));

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