HTML form input tag name element array with JavaScript

Question

This is a two part question. Someone answered a similar question the other day (which also contained info about this type of array in PHP), but I cannot find it.

1.) First off, what is the correct terminology for an array created on the end of the name element of an input tag in a form?

<form>

    <input name="p_id[]" value="0"/>
    <input name="p_id[]" value="1"/>
    <input name="p_id[]" value="2"/>

</form>

2.) How do I get the information from that array with JavaScript? Specifically, I am right now just wanting to count the elements of the array. Here is what I did but it isn't working.

function form_check(){
    for(var i = 0; i < count(document.form.p_id[]); i++){  //Error on this line

        if (document.form.p_name[i].value == ''){
            window.alert('Name Message');
            document.form.p_name[i].focus();
            break;
        }

        else{
            if (document.form.p_price[i].value == ''){
                window.alert('Price Message');
                document.form.p_price[i].focus();
                break;
            }

            else{
                update_confirmation();
            }
        }
    }
}

Answer 1

document.form.p_id.length ... not count().

You really should give your form an id

<form id="myform">

Then refer to it using:

var theForm = document.getElementById("myform");

Then refer to the elements like:

for(var i = 0; i < theForm.p_id.length; i++){

Answer 2

for(var i = 0; i < count(document.form.p_id[]); i++) {

For this line use like this,

var cntval = document.form.p_id.length;
for(var i = 0; i < cntval; i++) {

Answer 3

1.) First off, what is the correct terminology for an array created on the end of the name element of an input tag in a form?

"Confusing PHPism".

As far as JavaScript is concerned a bunch of form controls with the same name are just a bunch of form controls with the same name, and form controls with names that include square brackets are just form controls with names that include square brackets.

The PHP naming convention for form controls with the same name is sometimes useful (when you have a number of groups of controls so you can so things like:

<input name="name[1]">
<input name="email[1]">
<input name="sex[1]" type="radio" value="m">
<input name="sex[1]" type="radio" value="f">

<input name="name[2]">
<input name="email[2]">
<input name="sex[2]" type="radio" value="m">
<input name="sex[2]" type="radio" value="f">

) … but is mostly just confusing.

2.) How do I get the information from that array with JavaScript?

Get the "name of form control" property of the elements property of the form. Since the name of the form controls includes square brackets, you can't use dot notation and have to use square bracket notation. Since you have multiple elements with that name, it will be a collection rather then a single control, so you can loop over it with a standard for loop that makes use of its length property.

var myForm = document.forms.id_of_form;
var myControls = myForm.elements['p_id[]'];
for (var i = 0; i < myControls.length; i++) {
    var aControl = myControls[i];
}

Answer 4

Try this something like this:

var p_ids = document.forms[0].elements["p_id[]"];
alert(p_ids.length);
for (var i = 0, len = p_ids.length; i < len; i++) {
  alert(p_ids[i].value);
}