The problem of let declaring variables in ES6

read an article in ES6 today: 

var a = [];
for (let i = 0; i < 10; iPP) {
  a[i] = function () {
    console.log(i);
  };
}
a[6](); // 6
The

document says that in the above code, the variable I is declared by let, and the current I is only valid in this loop, so the I of each loop is actually a new variable, so the final output is 6.

but isn"t a [6] function () {console.log (i)}? When running a [6] (), since I is declared by let and is only valid in block-level scope, shouldn"t I print out undefined? How could it be six?

Javascript
May.05,2021

for each loop generates a new scope, and I in fuction accesses I within this scope, which can be understood like this: 

var a = [];
for (let i = 0; i < 10; iPP) {
  a[i] = function () {
    let j=i
    console.log(j);
  };
}
a[6](); // 6

you can use babel to escape the source code look at:

clipboard.png

coincidentally, I happen to have written an article on this question. You can take a look at it.
. Although I thought it was very clear at that time, after reading it now, I felt that I couldn't understand it. But it still means
my previous analysis of this problem < / A >

I is declared in outer curly braces. So the curly braces inside also take effect, and vice versa, which can be simply understood as passing down the scope

.

Previous: How to solve the stutter problem caused by PHPstorm scanning index?

Next: After rewriting the prototype object, why does the original prototype object still exist

css mysql arrays josn react html typescript webpack npm sass R objective-c .net sql-server jquery python-3.x angularjs django angular excel regex iphone ajax linux xml pandas vba spring database wordpress string wpf xcode windows bash postgresql oracle multithreading eclipse list firebase algorithm macos forms image scala visual-studio azure bootstrap spring-boot react-native python-2.7 docker performance function winforms matlab powershell apache dataframe api sqlite numpy rest shell selenium flutter dart maven loops qt swing android-studio csv express file class tensorflow sorting codeigniter perl
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-64f5-1b3b41d-2c276.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b3b41d-2c276.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
Need Help?