javascript - KOA2+node+ejs错误: Can't set headers after they are sent

Question

使用kOA2+node js+ajax抓取网页数据并在首页显示结果信息:

查询.js

const superagent = require('superagent');
const charset = require('superagent-charset');
const cheerio = require('cheerio');

charset(superagent);

function Rate(from, to, queryNumber) {
    this.from = from;
    this.to = to;
    this.queryNumber = queryNumber;
}

module.exports = Rate;

Rate.query = function query(rate, callback) {
    let URL = 'http://qq.ip138.com/hl.asp?from=' + rate.from + '&to=' + rate.to + '&q=' + rate.queryNumber;
    superagent.get(URL)
       .charset('gbk')
       .end((err, sres)=> {
          if (err) {
              return next(err);
          }
          var $ = cheerio.load(sres.text);
          var queryResult = [];
          queryResult[0] = $(".rate td").eq(4).text();
          queryResult[1] = $(".rate td").eq(5).text();
          callback(null, queryResult);

       })
};

<小时/>

index.js

const index = require('koa-router')();
const Rate = require('../models/query');

index.get('/s*', async (ctx, next) => {
    let rate = new Rate(ctx.query.from, ctx.query.to, ctx.query.queryNumber);
    await Rate.query(rate, (err, queryResult) => {
      if (err) {
         return next(err);
      } else {
         return ctx.render('query', {
                   title: '查询结果',
                   rate: queryResult[0],
                   amount: queryResult[1]
      });
      return next();
      }

    });

访问“/s*”页面时，出现:(Node: 808) UnhandledPromiseRejectionWarning: Unhandled hatrejection (rejection id: 1): Error: Can not set headers after they are sent.错误，页面无法跳转。

尝试了很多方法，还是不知道提前返回哪里。

现在知道了，因为ctx结束后，还要调用render来写入数据。 。但是那不是要改变的地方。请帮助我。

Answer 1

请更新

const index = require('koa-router')();
const Rate = require('../models/query');

index.get('/s*', async (ctx, next) => {
    let rate = new Rate(ctx.query.from, ctx.query.to, ctx.query.queryNumber);
    await Rate.query(rate, (err, queryResult) => {
      if (err) {
         return next(err);
      } else {
         return ctx.render('query', {
                   title: '查询结果',
                   rate: queryResult[0],
                   amount: queryResult[1]
      });
      return next();
      }

    });

到

const index = require('koa-router')();
const Rate = require('../models/query');

index.get('/s*', async (ctx, next) => {
    let rate = new Rate(ctx.query.from, ctx.query.to, ctx.query.queryNumber);
    await Rate.query(rate, (err, queryResult) => {
      if (err) {
         return next(err);
      } else {
         return ctx.render('query', {
                   title: '查询结果',
                   rate: queryResult[0],
                   amount: queryResult[1]
      });
      }

    });