Javascript array access in Internet Explorer

Question

I've a HTML code snippet like follows:

<form>
  <select name="mySelect">
    <option value="1">text_1</option>
    <option value="2">text_2</option>
  </select>
</form>

I found out that in Internet Explorer, Javascript below can work:

document.forms[0].mySelect.options(0).text

But in Firefox or Chrome, it can not work and reports such error message:

document.forms[0].mySelect.options is not a function

In my opinion, mySelect.options should be an array, thus must be accessed by mySelect.options[0]. I also checked the DOM api and found no options function available.

Does it mean in the IE javascript engine, all arrays can be treated as both a collection and a function? Any advice will be appreciated, thanks in advance!

Because IE confuses property access with method calls, use square brackets: ...options[0].text — RobG
– RobG, Commented Apr 10, 2014 at 6:13
It should be noted that referring to a form via document.forms[0] is a bad idea in principle as it will break the moment you decide to add another form to that page (like a login form, or a sidebar form). Much better off to use document.getElementById( 'FORMID' ).mySelect... — Tom McQuarrie
– Tom McQuarrie, Commented Apr 10, 2014 at 6:18
@TomMcQuarrie, thanks! Actually I know forms[0] is a bad idea and for me I only use JQuery to ignore such browser differences. This is a snippet from a legacy project which causes me a bit confused. — SmartekWorks
– SmartekWorks, Commented Apr 10, 2014 at 6:25
Related post - JavaScript array index 'undefined' in Internet Explorer — RBT
– RBT, Commented Jun 25, 2019 at 5:57

Teemu · Accepted Answer · 2014-04-10 06:35:03Z

2

Notice, that options is not an array, it's HTMLCollection, which is an array-like object. This is also a host object, hence it can behave differently from JS objects.

In IE you can call HTMLCollection as it was a function (at least in older IEs):

select.options(vIndex [, iSubIndex] );

Here vIndex is either an integer representing an index, or a string referring name property. As you can have multiple similar names, iSubIndex is used to construct a collection of all elements that have a name or id property equal to the string, and then retrieves from this collection the element at the position specified by iSubIndex.

answered Apr 10, 2014 at 6:35

Teemu

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1 Comment

SmartekWorks Over a year ago

noted and thanks, actually I also tested on IE11 and it can work. Guess IE also sticks to its tradition, :)

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