Question 327525 in Javascript Question posted in
A very good W3school tutorial can be found here.

Return a function from within a function in Javascript

This is what I tried:

var app = function() {
    var listen; 
    return listen = function()
        { 
            return "ggg";
        }
    }

console.log("dd: " + app().listen().length);

This says listen is not a function.
console.log("dd: " + app().listen().length);

Now w.r.t socket.io, we can write:

  const express = require('express');
  const app = express();
  app.listen();

I want to understand how to write like socket.io where from we can call one function from another?

Tags:

2

Answers


  1. 0

    you are returning an expression which returns undefined as somevar = ‘somevalue’ will give you undefined. instead you should

        return {
listen: function()
            { 
                return "ggg";
            }
    }
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  2. 0

    You seem to want to create a factory function. The problem is that you are calling it’s result as if it were an Object (with method listen). The way you created the function app returns a (named) function. See the snippet

    const app = function() {
  return listen = function() {
    return "ggg";
  };
}

const appFactory = function() {
  return {
    listen() {
      return "ggg";
    }
  };
}

// your function returns a function
console.log("dd: " + app()() + 
  ` => the returned function name is '${app().name}'`);

// the factory returns an object
// with method 'listen'
console.log("dd: " + appFactory().listen());
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