无法将链接从一个功能传递到另一个功能

Question

I've written a very small script in node.js using request and cheerio to parse titles connected to links which I've already scraped from it's landing page.

The problem is I can't find any idea as to how I can pass links (populated from the first function) to the second function in order to get the titles from there. I'm very new to node.js so can't figure out how to return the result from the first function and pass them to the latter one.

The error I'm having:

for (const link of links) {
                   ^
ReferenceError: links is not defined

This is the full script:

var request = require('request');
var cheerio = require('cheerio');

const url = 'https://news.ycombinator.com';

request(url, function (error, response, html) {
  if (!error && response.statusCode == 200) {
    var $ = cheerio.load(html);
    $('.title .storylink').each(function(){
    var links = $(this).attr("href");
    });
  }
});

for (const link of links) {
  (function(url) {
    request(url, function (error, response, html) {
      if (!error && response.statusCode == 200) {
        var $ = cheerio.load(html);
        var title = $('title').eq(0).text();
        console.log(title);
      }
    });
})(link);
}

Btw, the selectors used within the script are flawless. All I need to know is pass the result from one function to another.

Answer 1

Your 'links' var is out of scope. It is outside the callback in 'request'. Either have to turn request into a promise, use request-promise, or move the for loop into the function to keep links in scope.

https://www.npmjs.com/package/request-promise

https://scotch.io/courses/10-need-to-know-javascript-concepts/callbacks-promises-and-async

Answer 2

It seems I found myself a solution. It did the trick:

var request = require('request');
var cheerio = require('cheerio');

const url = 'https://news.ycombinator.com';

function getItems(callback){
  request(url, function (error, response, html) {
    if (!error && response.statusCode == 200) {
      var $ = cheerio.load(html);
      $('.title .storylink').each(function(){
      var links = $(this).attr("href");
      return callback(links,false);
      });
    }
  });
}
getItems((link)=>{
    request(link, function (error, response, html) {
      if (!error && response.statusCode == 200) {
        var $ = cheerio.load(html);
        var title = $('title').eq(0).text();
        console.log(title);
      }
    });
});