Optimizing performance for setting multiple inline css styles

Question

I'm doing a lot of

 element.css {
     style1: val1
     style2: val2
     ...
 }

using jQuery, and right now it's a performance bottleneck for me. Looking at jQuery's implementation, it seems to be setting each style individually, resulting in multiple modifications of the style attribute.

Presumably in this case, we only need to modify the style attribute once. However, I'm a little hesitant to re-implement .css. Has anyone done this already? If I do decide to reimplement it, are there going to be gotchas to be aware of?

how about adding/removing classes instead? That would also make the js-code much cleaner. — display-name-is-missing
– display-name-is-missing, Commented Jan 29, 2014 at 0:33
I'm generating the styles on the fly, otherwise that would be my first choice — josh
– josh, Commented Jan 29, 2014 at 0:36

Tibos · Accepted Answer · 2014-01-29 00:43:06Z

1

The biggest performance hit with setting styles comes from trashing the layout. That happens when you change an attribute that influences the layout (ex: width) and then immediately ask for information about the layout. If you don't do that (for example by batching the changes together), then setting the style one property at a time versus the whole style text at once is pretty much the same, as the rendering engine is pretty smart about that.

So instead of doing:

$('.myItem').each(
  $(this).css('width', $(this).css('width') + 10);
);

change to:

var widths = [];

$('.myItem').each(
  widths.push($(this).css('width'));
);

$('.myItem').each(
  $(this).css(widths.shift() + 10));
);

answered Jan 29, 2014 at 0:43

Tibos

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1 Comment

josh Over a year ago

I tried testing .css vs blazemonger's solution, and the improvement seems pretty marginal, so I think you're on target...

Blazemonger · Accepted Answer · 2014-01-29 01:00:38Z

0

Append a single string to the style attribute, then -- later styles will automatically override earlier ones.

$(el).attr('style',$(el).attr('style')+newStyleString);

However, if you can't perceive a performance hit in your web page, I wouldn't worry about it.

answered Jan 29, 2014 at 1:00

Blazemonger

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