When i create 2 functions in java script and initialize a variable A in function 1, can I use this variable in function2?

I am a beginner in java script, and I have got a problem here and would really appreciate the help.

I created a function called menu and I want to get a value from the user in an excel sheet and do an action based on that value in another function. So I have two questions:-

1- When i create 2 functions in java script and initialize a variable A in function 1, can I use this variable in function2? I couldn’t test that because I’m using google app script and I can only run one function.

2- (In the code) –> How to get the value from the use and use it in another function (If my first question is true). The value I’m trying to get is the wn, and i tried to Logger.log(wn) twice and they had the same values(348-372)!

function menu(){
        //get the good week number
        var date = new Date();
        var wn = [(Math.floor(WEEKNUMBER(date))+3).toFixed(0)]
        do {  
            wn.push((wn[wn.length-1]-1).toFixed(0))
        } while(wn[wn.length-1] != 348);
        var line = "<select style='width:60px;height:40px;' id='select'>"
        for ( var x in wn ) // thats the loop taht is going to show all the weeks for the user
          line +="<option>" + wn[x] + "</option>"
        line +="</select>"
        Logger.log(wn);
        var ui = SpreadsheetApp.getUi();
        var html = HtmlService.createHtmlOutputFromFile('Selector')
            .setWidth(200)
            .setHeight(150).setContent("<div>"+line + "</div><br>.  <div><button onclick='reset()'>Confirm</button> </div>.  <script>function  reset(){var wn = document.getElementById('select').value;document.getElementsByTagName('Body')[0].style.cursor = 'wait';google.script.run.withSuccessHandler(function (){google.script.host.close();}).readWP2(wn);}</script>")
        SpreadsheetApp.getUi() // Or DocumentApp or SlidesApp or FormApp.
            .showModalDialog(html, 'Please select a week number');
Logger.log(wn);
}

If you need more explanation please let me know