I read through similar topics, but couldn't find an answer.

Here is the code:

foo_arr = ["a", "b", "c"]
bar_arr = ["x", "y"]

test(bar_arr);
document.write(bar);

function test(arr_name) {
    bar = Math.random()*arr_name.length;

    if (bar < 1) {test(arr_name)}
}

As you can see I pass the array name to the function, but what if I need to pass a variable too? For instance

test(bar, bar_arr);

function test(var_name, arr_name) {
    var_name = Math.random()*arr_name.length;

It won't work. Why and how to do this?

I read through similar topics, but couldn't find an answer.

Here is the code:

foo_arr = ["a", "b", "c"]
bar_arr = ["x", "y"]

test(bar_arr);
document.write(bar);

function test(arr_name) {
    bar = Math.random()*arr_name.length;

    if (bar < 1) {test(arr_name)}
}

As you can see I pass the array name to the function, but what if I need to pass a variable too? For instance

test(bar, bar_arr);

function test(var_name, arr_name) {
    var_name = Math.random()*arr_name.length;

It won't work. Why and how to do this?

• javascript

Share Improve this question Follow asked Mar 2, 2011 at 16:28 Daniel J FDaniel J F 1,06422 gold badges1616 silver badges3131 bronze badges

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3 Answers 3

Sorted by: Reset to default 6

You cannot pass (references to) variables in JavaScript, only their values. Even with bar_arr, you are only passing the "value" of the array, which is an object -- you can modify the object's properties this way, but you can't change bar_arr itself.

To really "pass" a variable, take the above trick one step back and use the object which contains the variables as properties. In this case, that is the window object of which all global variables are a property:

function test(var_name) {
  window[var_name] = 'foo';
}

test('bar'); // note that the property name is a string, not a variable
alert(bar); // now the global 'bar' is set

If you want to set the value of only one global variable, you can return the wanted value from your fonction :

function test(arr_name) {
    return Math.random()*arr_name.length;
}

bar = test(bar_arr);

I'm really not sure that's what you want to do, but I'm glad if I was able to help.

If var_name is a global variable, you can still access it inside function test. Example:

var_name; // global
function test(arr_name) {
    var_name = Math.random()*arr_name.length;  // still accessible here

    if (bar < 1) {test(arr_name)}
}