Left offset of an inline element using jQuery

问题:

I have the following piece of HTML:

<div><p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor 
incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud 
exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in 
reprehenderit in voluptate velit <strong id="s">esse cillum dolore eu fugiat nulla pariatur.
Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.</strong></p></div>

The width of the DIV is fixed at 600px using CSS. Now, I want to find the offset().left of the <strong> element. So I did:

alert( $("#s").offset().left );

However this does not seem to produce the right value, as I can clearly see the strong element is seen half way through the 600px width, but the offset value I get is only 8px.

How do I find the offset().left value of the inline strong element?

回答1:

Here's what's happening:

Since the inline element spans multiple lines jQuery will give you the left-most position of that element, not the offset of the beginning of the element.

To get around this, try this plugin:

jQuery.fn.inlineOffset = function() {
    var el = $('<i/>').css('display','inline').insertBefore(this[0]);
    var pos = el.offset();
    el.remove();
    return pos;
};

The plugin will create a temporary element and insert it just before the target element - it will then return the offset of that temporary element.

Example usage:

alert( jQuery('strong').inlineOffset().left );

回答2:

The reason you are getting the result of 8px is because even though the element starts in half way through your container, since there's a line break its left edge is 8px in from the page.

I have one of those feelings that there's probably a much better way to do it than this, but the first thing I could think of to work around this problem is to insert another element right before the <strong> and check its position:

$("<span><span>").insertBefore($('#s')).offset();

回答3:

I believe offset is relative to the document, while position is relative to the parent.

http://docs.jquery.com/CSS/position