how can i get the value of variable inside function to outside the on jquery

can i take the value from ‘a = entry.username’ out of the function? i want to get value that already looping inside the function

$('#btnlogin').click(function(){
        var usernamelogin = $('#usernamelogin').val()
        var passwordlogin = $('#passwordlogin').val()
        var data_user1 = JSON.parse(localStorage.getItem('data_user'))
        
        for(var i in data_user1){
        var entry = data_user1[i]
        
        if(usernamelogin == entry.username && passwordlogin == entry.password){
            window.location.href = "curhat.jsp"
            a = entry.username
            return
            }   
        }
        if(usernamelogin != entry.username && passwordlogin != entry.password){
            alert("wrong username or password") 
        }
                
        //console.log(data_user1)
        //console.log('username = ' + entry.username)
        
    })