Is it possible to set the height/width of an element in percent using JavaScript or jQuery?
The question is what do you want the div's height/width to be a percent of?
By default, if you assign a percentage value to a height/width it will be relative to it's direct parent dimensions. If the parent doesn't have a defined height, then it won't work.
So simply, remember to set the height of the parent, then a percentage height will work via the css attribute:
obj.style.width = '50%';