call method of a function question.

[Tullamore]

I need to modify the last statement in the item_add_click function so it calls the update_display function by using the call method of that function. In this case, you don’t need to pass arguments because you don’t need to change the object that’s used for the this parameter. Here is my code:

var invoice = [];

var $ = function(id) { return document.getElementById(id); }

var update_display = function () {
    $("item_list").value = get_item_list(invoice);
    $("subtotal").value = get_subtotal(invoice).toFixed(2);
    $("sales_tax").value = get_sales_tax(invoice).toFixed(2);
    $("total").value = get_total(invoice).toFixed(2);

    $("item_code").value = "";
    $("item_name").value = "";
    $("item_cost").value = "";
    $("item_qty").value = "1";
    
    $("item_code").focus();
}    

var item_add_click = function() {
    var item = [];
    item["item_code"] = $("item_code").value;
    item["item_name"] = $("item_name").value;
    item["item_cost"] = parseFloat($("item_cost").value);
    item["item_qty"]  = parseInt($("item_qty").value);
    
    if ( item["item_code"] == "" ) return;
    if ( item["item_name"] == "" ) return;
    if ( isNaN(item["item_cost"]) ) return;
    if ( isNaN(item["item_qty"] ) ) return;

    invoice.push(item);
    update_display();
}

window.onload = function () {
    $("item_add").onclick = item_add_click;
    $("item_code").focus();
}

any and all help is very much appreciated. Thanks.

[Kor]

I need to modify the last statement in the item_add_click function so it calls the update_display function by using the call method of that function

What do you mean by "the method of a function"? There is no method defined there, and, anyway, methods can be defined as being properties of an object, or there is no object created there becuase you did not use that function as a constructor.

Can you detail a little bit your aim, please? I confess I did not understand which, in fact, is your problem.