How to get variables in another function from one function in JavaScript

the code is as follows 

$(function(){
    $(".a").on("click",function(){
        var counter=0
        counterPP
    })
    
    $(".b").on("click",function(){
        if(counter>=3){
            alert(3)
        }
    })
})

there are two buttons, an and b, click a, and the variable counter will increase by 1. When the b button is clicked, a prompt box will pop up if the variable counter is greater than or equal to 3.
because counter is not a global variable, it will be destroyed after each click, so every time counter is 1, how to implement it if you use a closure. If the global variable is no longer used, how should the countervalue in the a button function be obtained in the function clicked by the b button?

Javascript
Feb.28,2021

must be declared in the upper scope, such as this 

$(function(){

    (function() {
        var counter = 0;
        
        $('.a').on('click',function() {
            counterPP;
        });
        
        $('.b').on('click',function() {
            if(counter > 3) {
                alert('3');
            }
        });
    })();
})

because you wrap a layer with an anonymous function, the local variables defined in this anonymous function are valid in the child function, that is, you should: 

$(function(){
    var counter=0;
    $('.a').on('click',function(){
        counterPP;
    })
    
    $('.b').on('click',function(){
        if(counter>=3){
            alert(3);
        }
    })
})

your original listening function logic for a will cause counter to always be 1, because every time you enter it, you initialize it to 0 and then add 1.

Previous: The js object is sorted by the number of letters, such as var obj= {'axiomagento baaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'}

Next: How does autodesk forge automatically get accessToken (JS or c-sharp)

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-64f5-1eaeda9-5d027.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1eaeda9-5d027.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
Need Help?