相同代码的两个版本返回不同的结果

Question

The two code below look same but they give me different result in IE8. Do you have any idea about that?

$('#frameMain').load(function(){                                
    var bodyHeight = $(this.contentDocument).find('body').attr('scrollHeight');                
    var bodyHeight2 = document.getElementById('frameMain').document.body.scrollHeight;
});

Answer 1

This code refer to parent body, not child.

document.getElementById('frameMain').document.body.scrollHeight

It should be like this:

document.getElementById('frameMain').contentDocument.body.scrollHeight;