Hoisting¶

Hoisting means to bring up scope declaration variables. This mechanism occurs only for variables declared using the keyword var and function declaration. This means that we can call a function or use such a variable even before its declaration.

The following examples show this mechanism:

console.log(foo);
var foo = "Lorem ipsum";

In the above example, the console will display undefined.

In the next example:

foo = 'hello'
console.log(foo);
var foo = 'Lorem ipsum';
console.log(foo)

add = function(a, b) {
  return a + b;
}
console.log(add(2, 3)); // in the console screen we will see 5, although the add variable is declared in the next line of code
var add;

In turn, trying to use hoisting with the variable declared with the let:

console.log(foo);
let foo = "Lorem ipsum";

We get an error: Uncaught ReferenceError: Cannot access 'foo' before initialization.