Note: Elevation of variable declarations

Any variable declared within a scope will be attached to that scope.

We habitually put var a = 2; as a life, and in fact the JavaScript engine does not think so. It treats var A and a = 2 as two separate declarations, the first is the task of the compilation phase, and the second is the task of the execution phase.

This means that regardless of where the declaration in the scope appears, the process can be visually imagined as all declarations (variables and functions) will be "moved" to the top of their respective work before the code itself is executed, a process known as Ascension. The declaration itself is promoted, and the assignment operation, including the assignment of a function expression, is not promoted.

Note: Elevation of variable declarations