Node: how to change the value of variable after calling the function using tablesasjson?

[Alex1233456]

why the variable cannot be changed after calling the function?

this is my code:

const tabletojson = require('tabletojson');

var email ;

tabletojson.convertUrl(

    'https://myurl
    ,
    { stripHtmlFromCells: true },
    function(tablesAsJson) {


  email = tablesAsJson[2][7][1];
var result2 = tablesAsJson;
        console.log(result2);
        var Firstname;
        var lastname;
        Firstname = tablesAsJson[0][1][1]
        lastname = tablesAsJson[0][0][1]

        console.log("Hello Sir: "+Firstname + "  " +lastname + ".  your email is : " + email)

        console.log(email)// this prints the correct answer
    }
  );

> while trying to print email in out scope of the function 
its returning a blank text with console.log("the email is " + email);

[vsemozhetbyt]

email is assigned in a callback function after table-to-JSON conversion is complete. If you try to use it just after the tabletojson.convertUrl() call it is still undefined because the mentioned callback will be executed asynchronously in a future loop cycle.

See:
https://nodejs.org/en/docs/guides/blocking-vs-non-blocking/
https://nodejs.org/en/docs/guides/event-loop-timers-and-nexttick/

[Alex1233456]

@vsemozhetbyt the issue is that i need to use the result of the variable (email) after calling it in another function which is in another file.js therefore i need to grap the value of email and not to call the function. if i can to use return of the function as a variable its ok as well

[vsemozhetbyt]

If I understand correctly, you can only call the file.js function from the callback if you need to use email from the result of the conversion.

However, it seems tabletojson provides a Promise API, so you can use async/await to make the code simpler.

[vsemozhetbyt]

Something like this:

'use strict';

const tabletojson = require('tabletojson');

(async function main() {
  try {
    const url = 'https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes';
    const array = await tabletojson.convertUrl(url);
    console.log(array[1][0]);
  } catch (err) {
    console.error(err);
  }
})();

[mscdex]

General questions like this should be posted to the nodejs/help repo instead.

[Alex1233456]

@vsemozhetbyt thanks for this awesome solution. can i ask the last question before closing the issue please?

while trying to exports the main function and its result like this: module.exports.main = main;
module.exports.result = result; into another file.js like this var test3 = require('./test3')
test3.main();
console.log(test3.result)
its appearing that module.exports.main = main;
^

ReferenceError: main is not defined--- why that?

this is the new code (your edited code): 

'use strict';

const tabletojson = require('tabletojson');
var result;
(  async function main() {
  try {
    const url = 'https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes';
    const array = await tabletojson.convertUrl(url);
    result = array[1][0];
  } catch (err) {
    console.error(err);
  }
})();
module.exports.main = main;
module.exports.result = result;

console.log(result)

[vsemozhetbyt]

In my code, function main is not declared as a variable, it is used as named IIFE. That is why ReferenceError: main is not defined.

If you need to use this code as exported function from a module, you need something llike this:

test-module.js:

'use strict';

const tabletojson = require('tabletojson');

async function getTableAsArray(url) {
  try {
    return await tabletojson.convertUrl(url);
  } catch (err) {
    console.error(err);
  }
}

module.exports = {
  getTableAsArray,
};

test.js:

'use strict';

const testModule = require('./test-module.js');

(async function main() {
  try {
    const array = await testModule.getTableAsArray(
      'https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes'
    );
    console.log(array[1][0]);
  } catch (err) {
    console.error(err);
  }
})();

[bnoordhuis]

I'm closing this. Please move it to nodejs/help if follow-up is necessary.