Are the scoped variables deleted even in Javascript?

Question

In Javascript, whenever the block of a variable scope runs, all its variables are deleted (as they say around the site)...

(function() {
    var a = false;
})()

But then why when I call setTimeout to alert the value of a variable still recognizes? That is, variables are not deleted?

(function() {
    var a = true;
    setTimeout(function() {
        alert(a)
    }, 1000);
})()

Answer 1

In the Javascript there are two types of scope, which are global and local.

Global scope is when you define a variable outside the code block of a function, so the variable is accessible to all the code.

For example:

var variavelGlobal = 10;

function funcOne() {
   alert(variavelGlobal);
}

function funcTwo() {
   alert(variavelGlobal + 10);
}

funcOne();
funcTwo();

Local scope is when you define a variable within a function, so it is only accessible within that function.

For example:

function funcOne() {

   var variavelLocal = 10;

   alert(variavelLocal);
}

function funcTwo() {
   alert(variavelLocal + 10);//Um erro será lançado.
}

funcOne();
funcTwo();

Observing: Whenever variables are created in Javascript, consider using the reserved word var, because without its use within the scope of a function, the variables within it have become global.

For example:

function funcOne() {

   variavelLocal = 10;//Sem a palavra reservada 'var'.

   alert(variavelLocal);
}

function funcTwo() {
   alert(variavelLocal + 10);//Não será lançado um erro, pois 'variavelLocal' é global.
}

funcOne();
funcTwo(); 

To answer your question, the variables defined within the scope of a function only cease to exist outside the local scope, which is outside the function, in the global scope, so they are not accessible, but they always existed within the scope of the function where they were defined. When this function is executed and when this function finishes its execution they are deleted until the setTimeout end up.