相对div位置的偏移量不同

Question

I have following html, I'm getting topOffset of each div, but child div under position:relative div are taking unexpected offset , I can't remove position , any help/solution would be great.

I'm trying to set some js behavior on some randomly generating div with offset .

Note: I can only use javascript not jq .

 document.getElementById('demo').innerHTML = document.getElementById('div1').offsetTop + " " + document.getElementById('div2').offsetTop + " " + document.getElementById('div2-child').offsetTop; 

 * { box-sizing: border-box; } html, body { margin: 0; padding: 0; } #div1 { border: 1px solid #000; padding: 10px; position: relative; } #div2 { border: 1px solid #000; padding: 10px; margin-top: 5px; position: relative; } #div2-child { border: 1px solid #000; padding: 10px; margin-top: 5px; } 

 Lorem ipsum dolor sit amet, consectetur adipisicing elit. Quidem, harum, officia quam magni provident tempora debitis mollitia placeat ducimus atque nobis fugit voluptatibus nisi commodi doloremque hic perspiciatis sint odit? <div id="div1">Lorem ipsum dolor sit amet, consectetur adipisicing elit. Quidem, harum, officia quam magni provident tempora debitis mollitia placeat ducimus atque nobis fugit voluptatibus nisi commodi doloremque hic perspiciatis sint odit?</div> <div id="div2"> Lorem ipsum dolor sit amet, consectetur adipisicing elit. Quidem, harum, officia quam magni provident tempora debitis mollitia placeat ducimus atque nobis fugit voluptatibus nisi commodi doloremque hic perspiciatis sint odit? <div id="div2-child">Lorem ipsum dolor sit amet, consectetur adipisicing elit. Quidem, harum, officia quam magni provident tempora debitis mollitia placeat ducimus atque nobis fugit voluptatibus nisi commodi doloremque hic perspiciatis sint odit?</div> </div> <p id=demo></p> 

Answer 1

As mentioned in MDN HTMLElement.offsetTop returns position relative to the parent element . So in your example document.getElementById('div2-child').offsetTop returns top position relative to div2

So, if you want the position relative to window(viewport) you need to add child position with it's parent position like below:

document.getElementById('demo').innerHTML = document.getElementById('div1').offsetTop + " " + document.getElementById('div2').offsetTop + " " + (document.getElementById('div2-child').offsetParent.offsetTop + document.getElementById('div2-child').offsetTop);

or you could use element.getBoundingClientRect() as below:

document.getElementById('demo').innerHTML = document.getElementById('div1').offsetTop + " " + document.getElementById('div2').offsetTop + " " + (document.getElementById('div2-child').getBoundingClientRect().top);

Answer 2

/**
* Get the position of an element relative to the document body
*/
function absoluteOffset(el) {
  var offset = el.offsetTop
  var offsetParent = el.offsetParent
  if (offsetParent === document.body) {
    return offset
  }
  return offset + absoluteOffset(offsetParent)
}

 var div1 = document.getElementById('div1') var div2 = document.getElementById('div2') var div2Child = document.getElementById('div2-child') document.getElementById('demo').innerHTML = absoluteOffset(div1) + ' ' + absoluteOffset(div2) + ' ' + absoluteOffset(div2Child) /** * Get the position of an element relative to the document body */ function absoluteOffset(el) { var offset = el.offsetTop var offsetParent = el.offsetParent if (offsetParent === document.body) { return offset } return offset + absoluteOffset(offsetParent) } 

 * { box-sizing: border-box; } html, body { margin: 0; padding: 0; } #div1 { border: 1px solid #000; padding: 10px; position: relative; } #div2 { border: 1px solid #000; padding: 10px; margin-top: 5px; position: relative; } #div2-child { border: 1px solid #000; padding: 10px; margin-top: 5px; } 

 Lorem ipsum dolor sit amet, consectetur adipisicing elit. Quidem, harum, officia quam magni provident tempora debitis mollitia placeat ducimus atque nobis fugit voluptatibus nisi commodi doloremque hic perspiciatis sint odit? <div id="div1">Lorem ipsum dolor sit amet, consectetur adipisicing elit. Quidem, harum, officia quam magni provident tempora debitis mollitia placeat ducimus atque nobis fugit voluptatibus nisi commodi doloremque hic perspiciatis sint odit?</div> <div id="div2"> Lorem ipsum dolor sit amet, consectetur adipisicing elit. Quidem, harum, officia quam magni provident tempora debitis mollitia placeat ducimus atque nobis fugit voluptatibus nisi commodi doloremque hic perspiciatis sint odit? <div id="div2-child">Lorem ipsum dolor sit amet, consectetur adipisicing elit. Quidem, harum, officia quam magni provident tempora debitis mollitia placeat ducimus atque nobis fugit voluptatibus nisi commodi doloremque hic perspiciatis sint odit?</div> </div> <p id=demo></p>