when to use elem.style.left o r elem.offsetLeft

When you are trying to get the left valu开发者_Python百科e of an element, what is the difference between elem.style.left or elem.offsetLeft in javascript?

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the difference is that elem.offsetLeft is a computed value of left offset, calculated by browser even if you haven't specified explictly the same property via style and/or CSS, instead elem.style.left it's a get of property left of style attribute

try this code: http://jsfiddle.net/nnryG/

the computedValue is unitless, the style property is what you assigned in inline style.