Declare a variable in another scope

Question

Take a look at this cut off code:

main = function() {
  alert('This is ' + T);
}

caller = function() {
  var T = 'me';
  main();
}

caller();

as you can see, I want the main function to determine the value of the variable T, but the browser shows this error: T - undefined.

I can handle this error by changing the scope of the T variable to the global scope, or even pass the T variable to main, but for some reason I don’t want to use it, and I want to declare the T variable in the scope of the main function. Is this possible or not? How can I handle this scenario?

Thanks.

Answer 1

I think something like this can handle this.

main = function() {
  alert('This is ' + T);
}

caller = function() {
  var T = 'me';
  eval('var func = ' + main);
  func();
}

caller();

Answer 2

You have 3 options:

• declare T outside of both
• pass T to main (T) as parameter

Answer 3

T - caller, main, - T caller main

T

main = function(T) {
  alert('This is ' + T);
}

caller = function() {
  var T = 'me';
  main(T);
}

caller();

T , main main

Answer 4

, , .

- :

caller = function() {
  var T = 'me',
      main = function() {
        alert('This is ' + T);
      };
  main();
}

caller();

, , . this Function.prototype.call Function.prototype.bind:

main = function() {
  alert('This is ' + this);
}

caller = function() {
  var T = 'me';
  main.call(T);
}

caller();

main = function() {
  alert('This is ' + this);
}

caller = function() {
  var T = 'me',
      newMain = main.bind(T);
      newMain();
}

caller();

Answer 5

- , T, main caller. , ,

var pair = (function() { 
  var T;
  var main = function() { 
    alert('This is ' + T);
  };
  var caller = function() { 
    T = 'me';
    main();
  };
  return { 'main': main, 'caller': caller}
})();

pair.main(); // Call main
pair.caller(); // Call caller

Answer 6

T this

main = function() {
   alert('This is ' + this);
}

caller = function() {
   var T = 'me';
   main.call(T);
}

caller();

Answer 7

:

• T global;
• getter
• T

Answer 8

var T = '';
main = function() {
  alert('This is ' + T);
}

caller = function() {
  T = 'me';
  main();
}

caller();