为什么IE8在JS字符串concat中添加空格？

Question

I'm writing a quick script to show and hide a ul and its contents - basically a dropdown menu. Problem I'm having is in the code below, line 2:

    $('#mainMenu ul li').mouseenter(function() {
    var dropTab = 'ul.' + $(this).attr("id") + 'Dropdown';
    alert(dropTab);
    $(dropTab).slideToggle();
});

Works fine in FF, but in IE8 the dropTab string has whitespace between the second and third elements ie it outputs:

ul.someId                   Dropdown

when I'm looking for:

ul.someIdDropdown

Like I said, works fine in FF, but am curious as to where the whitespace is coming from, as it stops the function from performing...

Any suggestions welcome - happy to consider an alternative method

Answer 1

The whitespace is obviously coming from inside the $(this).attr("id") method. IE must not trim the id when it is returned. You may want to try changing that line to this:

var dropTab = 'ul.' + $.trim($(this).attr("id")) + 'Dropdown';