3. Variable declaration promotion?

Declaration and promotion of variables ：
Variable declarations are always silently declared by the interpreter “ promote ” To the top of the method body
Please note that , Variable assignments are not promoted , It's just that the statement has been elevated .

var num1=1; // Global variables , Scope is the current file
function testf1(){
num1=2; // local variable , The statement was elevated
var num1;
alert(num1); //2
}
function testf2(){
alert(num1); // Global variables 1
}