Christian Heilmann

Q&A: Dynamically assigning CSS Floating in JavaScript

Monday, April 2nd, 2007 at 5:09 pm

Q: I am creating some HTML elements using JavaScript and the DOM. All is fine, but I need to define one element as floated to the right. I tried var d=document.createElement(‘div’); d.setAttribute(‘float’,’left’); which seems to do it, but the element is not floated. I tried then to use the style collection with d.style.float = ‘left’; but that didn’t work either. How do you float an element in JS?

A: Your first approach was wrong, as this would add an attribute called “float� to the element and not set the CSS property. The second approach is almost right, but “float� is a reserved word in JavaScript (because of floating point numbers). The correct property of the style collection is called cssFloat (you will also run into the same issue when you try to create labels with a “for� attribute, this one is called htmlFor). This’ll work nicely in Firefox, but Internet Explorer does not support cssFloat (one of the annoying bugs that were still not fixed).

In any case, generating a lot of HTML and defining the style inside your JavaScript is not a very maintainable way of development. It is much easier to keep the annoying little browser CSS support glitches to fix in CSS rather than having to check through a script to find where you changed it. In order to allow for that all you need to do is assign either an ID or a class to the parent element of all your DIVs or add a CSS class to the DIV when you create it. Then you can define the floating in CSS and you don’t need to worry about it any longer. Be aware that you need to use the className property (d.className = ‘foo’) to assign a CSS class to an element and not setAttribute(‘class’,’foo’) as class is another reserved word.

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