CODEWITHSUNDEEP
javascriptclosures
souparno majumder
souparno majumder

Reputation: 2052

javascript create predefined private variable inside a function dynamically

I am trying to create a predefined private variable inside a function dynamically. The concept I am using, is function return from within a closure block Like this:-

var bar = (function (){
  var foo = "Hello World";
    return function () {
    console.log(foo);
  } 
}());

bar();

This is the code that i am using to create an equivalent dynamic expression of the above execution

var createClosure = function(fn) {
  var __fn = function () {
    var foo = "Hello World";
    return fn;
  }
  return __fn();
}

var bar = createClosure(function () {
  console.log(foo);
});

bar();

but running the above code gives me ReferenceError: foo is not defined What should be the equivalent representation of a function return from a closure block?

Upvotes: 0

Views: 55

Answers (2)

souparno majumder
souparno majumder

Reputation: 2052

Here is an way out that I have found, let me know, if this is the correct approach.

var createClosure = function(fn) {
  var __fn = function () {
    var foo = "Hello World";
    var entire = fn.toString();
    var body = entire.substring(entire.indexOf("{") + 1, entire.lastIndexOf("}"));
    return function () {
      eval(body);
    }
  }
  return __fn();
}

var bar = createClosure(function () {
  console.log(foo);
});

bar();

Upvotes: -1

mash
mash

Reputation: 2526

This is as close as you can get:

function createClosure(fn) {
  const baz = {};
  baz.foo = "Hello World";
  return () => fn(baz);
}
const bar = createClosure(baz => console.log(baz.foo));

bar();

Or just pass in foo as an argument directly. But you can not just make foo exist in another scope. So you could obviously make it global but that wouldn't be a good idea either.

Upvotes: 2

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