Javascript: Get all elements with id id[x]

Question

Using javascript how do I get the number of elements present with the id of id[x]?

Sample HTML:

<input name="vrow[0]" id="vrow[0]" value="0" type="text"/>
<input name="vrow[1]" id="vrow[1]" value="0" type="text"/>
<input name="vrow[2]" id="vrow[2]" value="0" type="text"/>
<input name="vrow[3]" id="vrow[3]" value="0" type="text"/>

The above html is generated depending on user input. How do I detect how many elements are present using javascript?

Currently I can detect presence of an element like this

Sample Javascript

if(document.getElementById('vrow[0]')){
var row=0;
    }
if(document.getElementById('vrow[1]')){
row=1;
    }
...

Answer 1

[] are not valid characters in ID attributes in HTML4.01. Even in HTML5, however, you should use the name attribute (without the numeric indexes), and then use getElementsByName():

<input name="vrow" value="0" type="text"/>
<input name="vrow" value="0" type="text"/>
<input name="vrow" value="0" type="text"/>
<input name="vrow" value="0" type="text"/>

var vrows = document.getElementsByName("vrow");
alert(vrows.length);

Note that older versions of IE and Opera may return elements with id attributes that have the same value as the name specified in getElementsByName(). IE may also return non-input elements with a name attribute that has the same value.