How to fix TypeError: value is not a function or its return value is not a promise in Node.js

// Check if value is actually a function
console.log('Type:', typeof myValue);
console.log('Value:', myValue);

// For promises, check if it's thenable
console.log('Is thenable:', myValue && typeof myValue.then === 'function');

// Wrong - missing executor function
const myPromise = new Promise();

// Correct - provide executor function
const myPromise = new Promise((resolve, reject) => {
  // Your async operation here
  setTimeout(() => {
    resolve('Success!');
  }, 1000);
});

// Wrong - returning non-promise in chain expecting promises
fetchData()
  .then(data => {
    return data.id; // Returns a number, not a promise
  })
  .then(fetchUserById); // Expects a promise, gets a number

// Correct - explicitly return a promise
fetchData()
  .then(data => {
    return Promise.resolve(data.id);
  })
  .then(id => fetchUserById(id));

// Better - let the function handle the promise
fetchData()
  .then(data => fetchUserById(data.id))
  .then(user => console.log(user));

// Wrong - missing semicolon can cause issues
const express = require('express')
(async () => {
  // This looks like you're trying to call express as a function
})()

// Correct - add semicolon
const express = require('express');
(async () => {
  // Now correctly interpreted as separate statements
})();

// Wrong - async function not returning a promise
async function getData() {
  const data = fetchSomething(); // Missing await
  return data.value; // data might not be resolved yet
}

// Correct - properly await promise resolution
async function getData() {
  const data = await fetchSomething();
  return data.value;
}

// Also correct - return the promise directly
async function getData() {
  return fetchSomething().then(data => data.value);
}

// Wrong - typo in method name
const result = myObject.proces(); // Should be 'process'

// Check if method exists before calling
if (typeof myObject.process === 'function') {
  const result = myObject.process();
} else {
  console.error('process method does not exist');
}