node.js http.get请求返回的中文乱码， iconv zlib模块都不好使，求解决！！！

Question

请求的接口是："http://club.jd.com/comment/productPageComments.action?callback=fetchJSON_comment98vv125475&productId=1993092&score=0&sortType=5&page=2&pageSize=10&isShadowSku=0&rid=0&fold=1"
网页显示中文正常，返回来的数据中文乱码

const http=require("http");

const fs=require("fs")

// const cheerio=require("cheerio")

// const iconv=require("iconv");

var url="http://club.jd.com/comment/productPageComments.action?callback=fetchJSON_comment98vv125475&productId=1993092&score=0&sortType=5&page=2&pageSize=10&isShadowSku=0&rid=0&fold=1";

http.get(url,function (res) {

    var html="";

    // iconv.decode(res, 'gb2312')

    res.setEncoding("utf-8");

    res.on("data",function(chunk){

        //console.log(chunk.toString())

        html+=chunk;

    });

    res.on("end",function(){

        fs.writeFile("./评价.txt",a,function(){

            console.log("完成")

        })

    });

    res.on("err",function(){

        console.log(err)

    })

})