Global Variable in javascript issue

Question

I've got a variable named allow which I want to be global, so any other function will be able to use it. What happens is, when I call the variable from a certain function, it returns undefined.

Here's my code:

var allow = null;

$('#form').submit(function(e) {
    error_found = false;

    $('#text').click();


    console.log(window.allow);

    if(window.allow == false) {
        alert('מספר הסדר שהוזן הינו בשימוש, נא בחר מספר אחר, או סדר את רשימת הסדר מחדש.');
        $("#order").focus();
        e.preventDefault();
        error_found = true;
    }

    if($("#fix_rel").val() == "" && !error_found){
        alert('נא בחר זמן יחסי או קבוע.');
        $("#fix_rel").focus();
        e.preventDefault();
    }

    if($("#fix_rel option:selected").val()=="rel" && !error_found){
        if(!$.isNumeric($("#order").val())){
            alert('מספר הסדר חייב להיות מספר!');
            $("#order").focus();
            e.preventDefault();
        }

    }
});


$('#text').click(function() {
    table = $("#table").val();
    order = $("#order").val();
    $.post('test.php',{table:table,order:order}).done(function(data) {
        if(data == "true") {
            window.allow = true;
        } 
        if(data == "false") {
            window.allow = false;
        }
        console.log(window.allow);
    });
}); 

I've been trying to solve it for the past 2 hours, and so far, I have NO clue.

Thanks in advance!

Answer 1

If you do this:

var allow = null;
console.log(window.allow);

and you don't see null in the console, then the ONLY possible explanation is that your definition of allow is not a global variable because there is some sort of outer function (such as $(document).ready() function or something like that.

If there is intervening code between the two statements, then additional possibility is that some other code is changing the value of the allow variable.

---

When you use var in front of a variable declaration, it defines that variable in the current scope. If the current scope is global, then the variable is a global variable. If the current scope is inside of a function, then that variable is defined as a local variable to that function.

---

You can probably fix your issue in one of two ways depending upon what you are trying to accomplish.

1. You can declare your variable in the actual global scope so it becomes a global variable.
2. You can assign your variable it's initial value with window.allow = null and not declare it otherwise. This will make it global no matter where you put this statement.
3. You can let the variable be a local variable and refer to it only as allow, not as window.allow when using it.

Answer 2

Use only allow instead of window.allow.

Like:

console.log(window);

instead of

console.log(window.allow);