call function inside another function javascript

Question

why this InsertToDataBase.insertdatatolamp0(1,1); insert the element into the database but the first one InsertToDataBase.insertdatatolamp0(0,0); did not.

please any solution to make the run InsertToDataBase.insertdatatolamp0(0,0);

main.js

const axios = require('axios')
const InsertToDataBase = require("./InsertToDataBase");
const username = 'admin'
const password = 'admin'
const token = Buffer.from(`${username}:${password}`, 'utf8').toString('base64')
const urlLAMP_0 = 'http://127.0.0.1:8282/~/mn-cse/mn-name/LAMP_0/DATA/la'
function getDataLAMP_0(){
  axios.get(urlLAMP_0, {
    headers: {
      'Authorization': `Basic ${token}`,
      'Accept': 'application/json',
      'mode': 'cors',
      'credentials': 'include',
      }
  })
  .then(function(response) {
        document.getElementById("rn0").textContent = response.data['m2m:cin'].rn;
        document.getElementById("ty0").textContent = response.data['m2m:cin'].ty;
  })
  .then((response) => {
    var rn0 = response.data["m2m:cin"].rn;
    var ty0 = response.data["m2m:cin"].ty;
    InsertToDataBase.insertdatatolamp0(0,0);
  });
}
InsertToDataBase.insertdatatolamp0(1,1);
getDataLAMP_0();

InsertToDataBase.js

const {Client} = require('pg')
const client = new Client({
    user:"postgres",
    password:"admin",
    host:"localhost",
    port:"5432",
    database:"postgres",
})
function insertdatatolamp0(rn0,ty0){
client.connect()
.then(()=>console.log("connected successfuly"))
.then(()=>client.query("insert into lamp0 values ($1,$2)",[rn0,ty0]))
.catch(e=> console.log(e))
.finally(()=> client.end())
}
module.exports = { insertdatatolamp0 };

Your function is asynchronous, it may not be making it to the end of your then chain. — Rawley Fowler
– Rawley Fowler, Commented Oct 12, 2021 at 19:01
yes it's running, I just miss copying getDataLAMP_0(); from the last line of the code — Badr-Eddine El mostaine
– Badr-Eddine El mostaine, Commented Oct 12, 2021 at 19:16

tao · Accepted Answer · 2021-10-12 19:28:46Z

2

In a promise chain, each step expects the result to be returned by the previous step.

In your promise chain, this step:

.then(function(response) {
  document.getElementById("rn0").textContent = response.data['m2m:cin'].rn;
  document.getElementById("ty0").textContent = response.data['m2m:cin'].ty;
})

does not return anything, which means it returns undefined. Therefore, the next step in the chain gets that response:

.then((response) => { // response here is undefined
  var rn0 = response.data["m2m:cin"].rn;
  var ty0 = response.data["m2m:cin"].ty;
  InsertToDataBase.insertdatatolamp0(0,0);
});

To make it work as expected, change the previous step to:

.then(function(response) {
  document.getElementById("rn0").textContent = response.data['m2m:cin'].rn;
  document.getElementById("ty0").textContent = response.data['m2m:cin'].ty;
  return response;
})

Side note: although InsertToDataBase.insertdatatolamp0(0,0); is higher up in code, you should not refer to it as "the first one". Because it's wrapped in a Promise() it will actually get executed later, when the promise resolves. Whereas InsertToDataBase.insertdatatolamp0(1,1); will be the first one executed.

edited Oct 12, 2021 at 19:28

answered Oct 12, 2021 at 19:20

tao

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3 Comments

Badr-Eddine El mostaine Over a year ago

I added a``` return response;``` but still did not run

tao Over a year ago

Maybe there's something wrong with your axios call. Place a logger inside the first step to make sure that code is executed. When you want to find out if a function is being called and from where, console.trace() will help you trace the chain of calls back to its source. In your case, you should place a tracer inside insertdatatolamp0 function itself.

tao Over a year ago

@Badr, also check the network tab in your browser to see if the axios call is being made and what's the response. An axios call only executes its .then() if no error is being thrown.

Roman Kurbatov · Accepted Answer · 2021-10-12 19:21:02Z

Do you see the result of your call

axios.get(urlLAMP_0, {
    headers: {
      'Authorization': `Basic ${token}`,
      'Accept': 'application/json',
      'mode': 'cors',
      'credentials': 'include',
      }
  })

in the Networks tab of your browser?

.then() chain works only if your initial promise succeeds. If your requests hangs while on waiting state or fails, the chain never conitnues.

Also, there is a problem further in your chain

.then(function(response) {
        document.getElementById("rn0").textContent = response.data['m2m:cin'].rn;
        document.getElementById("ty0").textContent = response.data['m2m:cin'].ty;
  })
  .then((response) => {
    var rn0 = response.data["m2m:cin"].rn;
    var ty0 = response.data["m2m:cin"].ty;
    InsertToDataBase.insertdatatolamp0(0,0);
  });

response in first function is the result of the axios.get() promise. But as your first .then() returns nothing (it should return either promise or some value) it is treated as your function returning undefined by default, so second .then(response => ...) will get undefined response.

You have two options.

Return response as a result of your first .then() or
Combine first and second .then() clauses in one function.

2 is cleaner and better, you should use several .then()'s if only you return Promise in each of then to move further or you need some condition, like:

return axios.get(something)
  .then(response => {
     if (response.a) return axios.get(somethingElse)
     else return response
  })
  .then(response => {
    // here we have either initial response or response from the next get
  })

That is not realted directly to your question, but it's a bug.

yes see the result of the call and I added a``` return response;``` but still did not run

Harrison Cramer · Accepted Answer · 2021-10-12 19:23:20Z

Right now, you are "chaining" the insertion of the data using a series of .then() statements.

However, you are not passing the response down through this chain of .then calls, which could be your issue.

When writing promises in Javascript, you should also try to handle your errors. That will give you more information about what could be going wrong, otherwise Javascript will throw an uncaught exception error and it'll be difficult to debug.

I've added a few lines of code to your main.js file, that will hopefully point you in the right direction.

const axios = require('axios')
const InsertToDataBase = require("./InsertToDataBase");
const username = 'admin'
const password = 'admin'
const token = Buffer.from(`${username}:${password}`, 'utf8').toString('base64')
const urlLAMP_0 = 'http://127.0.0.1:8282/~/mn-cse/mn-name/LAMP_0/DATA/la'
function getDataLAMP_0(){
  axios.get(urlLAMP_0, {
    headers: {
      'Authorization': `Basic ${token}`,
      'Accept': 'application/json',
      'mode': 'cors',
      'credentials': 'include',
      }
  })
  .then(function(response) {
        document.getElementById("rn0").textContent = response.data['m2m:cin'].rn;
        document.getElementById("ty0").textContent = response.data['m2m:cin'].ty;
        return response; // You must return the response here....

  })
  .then((response) => { // In order to get access to it here...
    // If you try to access response.data (where response === undefined) you will get an error! That may be happening, but you weren't handling the error.
    var rn0 = response.data["m2m:cin"].rn;
    var ty0 = response.data["m2m:cin"].ty;
    return InsertToDataBase.insertdatatolamp0(0,0);  
  })
  .then(() => {
    console.log("SUCCESS");
  })
  .catch((err) => { // And handle your error case!
    console.error(err);
   });
}
getDataLAMP_0();

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