Non-repeating stack in JavaScript

Question

I need to keep a stack of 10 items (value primitives, not objects) where no item is repeated. Here's my initial stab at an implementation. Any suggestions for improvements?

var items = [];

function newItem() {
    return Math.floor(Math.random() * 50);
}

function inArray(arr, val) {
    var in_arr, i;
    in_arr = false;
    i = arr.length;
    if (i < 1) {
        return in_arr;
    }
    do {
        if (arr[i - 1] === val) {
            in_arr = true;
            break;
        }
    } while (--i);
    return in_arr;
}

function addItem() {
    var new_item;
    while (items.length > 9) {
        items.shift();
    }
    do {
        new_item = newItem();
    } while (inArray(items, new_item));
    items.push(new_item);
}

Answer 1

while (items.length > 9) {
    items.shift();
}

can be written without iteration as

var len = items.length;
if (len > 9) {
    items = items.slice(len - 9);
}

Since JS 1.6, inArray can be written as array.indexOf(element) != -1. Otherwise,

if (i < 1) {
    return in_arr;
}
do {
    if (arr[i - 1] === val) {
        in_arr = true;
        break;
    }
} while (--i);
return in_arr;

can be written more simply as

while (i--) {
    if (arr[i] === val) {
        return true;
    }
}
return false;