IE7 - issue with javascript

Question

I have an issue only on old IE explorers with this js code:

var elements = [
        {'name':'manuscript_file', 'filetype':/(\.|\/)(doc|docx|txt|odt|zip|rar|rtf|gz|tar|bz2|bz|7z|tex)$/i},
        {'name':'presentation_file', 'filetype':/(\.|\/)(pdf)$/i},
        {'name':'figures_file', 'filetype':/(\.|\/)(pdf|png|jpg|gif|zip|rtf|eps)$/i},
        {'name':'graphical_file', 'filetype':/(\.|\/)(pdf|png|jpg|gif)$/i},
        {'name':'supplementary_file', 'filetype':/(\.|\/)(zip)$/i},
        {'name':'non_published_material', 'filetype':/(\.|\/)(doc|docx|zip|pdf)$/i},
    ]
    , url = $('form').attr('action');



$.each(elements, function(i, element) {
    $('#form_' + element.name).val('');
    $('#form_' + element.name).prev('button').removeAttr('disabled')
    ...

On the line with

 $('#form_' + element.name).val('');

IE7 is telling me

Message: 'name' is null or not an object

Any idea? Thx.

What happens if you use element.getAttribute('name') instead of element.name? — Paul S.
– Paul S., Commented Nov 11, 2014 at 16:36
I don't know why, but in my case, in the first iteration, the variable element is the array elements itself. Just added if (element) to get rid of the error. — DontVoteMeDown
– DontVoteMeDown, Commented Nov 11, 2014 at 16:36
What version of jQuery do you use? And yes what @PaulS. said or, as an alternative $(element).attr('name') is used ? — Comfortably Numb
– Comfortably Numb, Commented Nov 11, 2014 at 17:22

Sampson · Accepted Answer · 2014-11-11 18:27:54Z

4

The problem here is with your trailing comma in the array of elements. Internet Explorer 7 is incorrectly interpreting a value to the right of the last comma. This makes the length n+1, thus causing jQuery to evaluate a null value on its last cycle:

var elements = [
    { 'name': 'manuscript_file' },
    { 'name': 'non_published_material' }, <--
]

You can see this confirmed by looping over two arrays; one with a trailing comma, and one without. Open http://jsfiddle.net/jonathansampson/mqntjbky/show/ in IE 7 for confirmation.

(function () {

    var elements = [
        { name: "Foo" }, 
        { name: "Bar" }
    ];

    var alternatives = [
        { name: "Fizz" }, 
        { name: "Buzz" },
    ];

    // This $.each will not throw an exception
    $.each( elements, function create ( i, element ) {
        try {
            $( "<div></div>" ).text( element.name ).appendTo( "body" );
        } catch ( e ) { alert( "Top fail: " + e.message ) }
    });

    // This $.each WILL throw an exception
    $.each( alternatives, function create ( i, element ) {
        try {
            $( "<div></div>" ).text( element.name ).appendTo( "body" );
        } catch ( e ) { alert( "Bottom fail: " + e.message ) }
    });

}());

Note below that the "Top fail" message is never raised, as it is in the block looping the collection that lacks a trailing comma. The "bottom fail" message, however, is in the affected block, and thus is raised during iteration.

enter image description here

edited Nov 11, 2014 at 18:27

answered Nov 11, 2014 at 18:19

Sampson

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2 Comments

Bergi Over a year ago

I don't have IE 7 at hand. What does it show? element is undefined in the last call?

Milos Cuculovic Over a year ago

Excellent answer, and it works as a charm. Thanks a lot.

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