Why is this result undifined?

var xx = 99;
function a(){
    alert(xx);
    var xx = 100;
}
a();
functionvar
Mar.18,2021

both the function declaration and the variable declaration are in advance, and the function declaration comes before the variable declaration, so the code is equivalent to:

  

variable declaration promotes to know.

MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b38818-4115d.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b38818-4115d.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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