How to solve promise issue?

I am new to Promise concepts and trying to wrap my head around but now I`` am confused here

const request = require("request");
const cheerio = require("cheerio");
const XMLHttpRequest = require("xmlhttprequest").XMLHttpRequest;
var url = require("url");


module.exports = {

    resturant: resturant,

};


var resturanttables = [];

function resturant(url, day) {

    return new Promise(function(resolve, reject) {
        request(url, function(error, response, html) {

            if (error) {
                return reject(error);

            } else if (response.statusCode !== 200) {

                return reject("Something is wrong! CINEMA")

            }
            httplogin("zeke", "coys", url, day);
            console.log(resturanttables, "i am here");

            resolve(resturanttables);

        });



    });
}

function httpafterlogin(url, cookie, day) {

    request.get({
            headers: {
                'content-type': 'text/html',
                'Cookie': cookie
            },
            url: url,
        },

        function(error, response, body) {



            console.log(day)
            var $ = cheerio.load(body);

            if (day === "Friday") {
                $(".WordSection2 p  span ").each(function(li) {
                    //  console.log(day, $(this).text())
                    resturanttables.push($(this).text());

                    console.log(resturanttables, "nside");
                });

            } else if (day === "Saturday") {
                $(".WordSection4 p span").each(function(li) {

                    resturanttables.push($(this).text())
                });

            } else {
                $(".WordSection6 p span").each(function(li) {

                    resturanttables.push($(this).text())


                });

            }

        });

}

function httplogin(username, password, urls, day) {

    request.post({
        headers: {
            'content-type': 'application/x-www-form-urlencoded'

        },
        url: urls,
        form: {
            "username": username,
            "password": password


        }
    }, function(error, response, body) {
        var cookie = response.caseless.dict['set-cookie'][0];
        var location = response;

        console.log(response.statusCode);
        cookie = cookie.substring(0, cookie.indexOf(';'));

        // httpafterlogin('http://vhost3.lnu.se:20080/dinner/'+response.headers.location, cookie);
        var newurls = url.resolve(urls, response.headers.location)
        httpafterlogin(newurls, cookie, day);

        // console.log(response.headers, "jdjdjjdjdjjdjdjdjjdjjdjdj")

    });

}

and then I call the function

loadPage.resturant("http://vhost3.lnu.se:20080/dinner/login", "Friday").then(function(data) {
    console.log(data, "did it work now ")
})

the problem is that it returns the empty array. But when i tried to check and console.log in the afterlogin function and i could see that the array was actually filled, but that code runs after the promise has been resolved. IN SHORT: how can I bound the resolve in restaurant promise not to send the data until the login function is completed?

in other words how can i get the filled array with information from afterlogin funtion?

Upvotes: 0

Answers (3)

thedarklord47

Reputation: 3322

rewrite httplogin and httpafterlogin to return promises:

function httpafterlogin (url, cookie, day) {
    return new Promise(function (resolve, reject) {
        request.get({
            headers: {
                'content-type': 'text/html',
                'Cookie': cookie
            },
            url: url
        }, function (error, response, body) {
            if (error) {
                reject(error);
            } else {
                resolve(body);
            }
        });
    }).then(function (body) {
        console.log(day);
        var $ = cheerio.load(body);

        if (day === "Friday") {
            $(".WordSection2 p span").each(function (li) {
                //  console.log(day, $(this).text());
                resturanttables.push($(this).text());
                console.log(resturanttables, "nside");
            });
        } else if (day === "Saturday") {
            $(".WordSection4 p span").each(function (li) {
                resturanttables.push($(this).text());
            });
        } else {
            $(".WordSection6 p span").each(function(li) {
                resturanttables.push($(this).text());
            });
        }
    });
}


function httplogin(username, password, urls, day) {
    return new Promise(function (resolve, reject) {
        request.post({
            headers: {
                'content-type': 'application/x-www-form-urlencoded'
            },
            url: urls,
            form: {
                "username": username,
                "password": password
            }
        }, function(error, response, body) {
            if (error) {
                reject(error);
            } else {
                resolve(response);
            }
        });
    }).then(function (response) {

        var cookie = response.caseless.dict['set-cookie'][0];
        var location = response;

        console.log(response.statusCode);
        cookie = cookie.substring(0, cookie.indexOf(';'));

        var newurls = url.resolve(urls, response.headers.location)
        return httpafterlogin(newurls, cookie, day);
    });
}

then use .then like rsp suggested:

function resturant(url, day) {

    return new Promise(function(resolve, reject) {
        request(url, function(error, response, html) {
            if (error) {
                return reject(error);
            } else {
                resolve(response);
            }
        })
    }).then(function (response) {
        if (response.statusCode !== 200) {
            throw new Error("Something is wrong! CINEMA");     
        }
        return httplogin("zeke", "coys", url, day)
    }).then(function () {
        console.log(resturanttables, "i am here");
        return resturanttables;
    });
 }

this way, the block containing resolve(restautanttables) will not get called until httplogin completes

Upvotes: 1

Dan Nagle

Reputation: 5425

Use promises throughout your code - you can simplify your code using the request-promise package in place of the request package. All requests become promises and the code is easier to read and maintain.

const rp = require("request-promise");
const cheerio = require("cheerio");
const url = require("url");

function resturant(url, day) {
  rp(url)
    .then(function(){
      // URL returned a 200 response
      // so attempt to perform login
      httplogin("zeke", "coys", url, day)
        .then(function (data) {
          // Promise is resolved here
          return data;
        });
    })
    .catch(function(error){
      // just throwing the error
      throw error;
    });
}

function httplogin(username, password, urls, day) {
  var options = {
    headers: {
      "content-type": "application/x-www-form-urlencoded"
    },
    uri: urls,
    form: {
      username: username,
      password: password
    },
    method: "POST",
    resolveWithFullResponse: true
  };
  rp(options)
    .then(function (response) {
      // POST succeeded
      // grab the cookie
      var cookie = response.caseless.dict['set-cookie'][0]
                           .substring(0, cookie.indexOf(';'));
      // get new url string
      var newurls = url.resolve(urls, response.headers.location);

      httpafterlogin(newurls, cookie, day)
        .then(function (tables) {
          return tables;
        })
        .catch(function (error) {
         // just throwing the error
         throw error;
        });

    })
    .catch(function (error) {
      // Login failure
      // just throwing the error
      throw error;
    });
}

function httpafterlogin(url, cookie, day) {
  var options = {
    headers: {
      "content-type": "text/html",
      "Cookie": cookie
    },
    uri: url,
    transform: function (body) {
      return cheerio.load(body);
    }
  };
  rp(options)
    .then(function ($) {
      // body has been transformed and
      // can now be processed with jQuery

      // initialise the tables array
      var tables = [];

      // DRY code
      // set default selector
      var selector = ".WordSection6 p span";
      // change the selector for Friday/Saturday
      if (day === "Friday") {
        selector = ".WordSection2 p  span ";
      } else if (day === "Saturday") {
        selector = ".WordSection4 p span";
      }
      // process the selected section
      $( selector ).each(function(li) {
        tables.push($(this).text())
      });

      // crawling complete
      return tables;
    })
    .catch(function (error) {
      // Crawling failure
      // just throwing the error
      throw error;
    });
}

Upvotes: 0

rsp

Reputation: 111466

If you don't want the promise to get resolved before the login is completed then you will either have to make your httplogin function take a callback and run it like this:

httplogin("zeke", "coys", url, day, function (err) {
  if (err) {
    reject(err);
  } else {
    resolve(resturanttables);
  }
});

or make it return a promise and run it for example like this:

httplogin("zeke", "coys", url, day).then(function () {
  resolve(resturanttables);
}).catch(function (err) {
  reject(err);
});

There are more ways to do it with promises but this is the simplest way.

Either way you have to make your httplogin function signal its completion by either calling the callback that it takes as an argument or resolving the promise that it returns.

Upvotes: 0

How to solve promise issue?

Answers (3)

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