Save object states in .data or attr - Performance vs CSS?
- by Neysor
In response to my answer yesterday about rotating an Image, Jamund told me to use .data() instead of .attr()
First I thought that he is right, but then I thought about a bigger context... Is it always better to use .data() instead of .attr()? I looked in some other posts like what-is-better-data-or-attr or jquery-data-vs-attrdata
The answers were not satisfactory for me...
So I moved on and edited the example by adding CSS. I thought it might be useful to make a different Style on each image if it rotates. My style was the following:
.rp[data-rotate="0"] {
border:10px solid #FF0000;
}
.rp[data-rotate="90"] {
border:10px solid #00FF00;
}
.rp[data-rotate="180"] {
border:10px solid #0000FF;
}
.rp[data-rotate="270"] {
border:10px solid #00FF00;
}
Because design and coding are often separated, it could be a nice feature to handle this in CSS instead of adding this functionality into JavaScript. Also in my case the data-rotate is like a special state which the image currently has. So in my opinion it make sense to represent it within the DOM.
I also thought this could be a case where it is much better to save with .attr() then with .data(). Never mentioned before in one of the posts I read.
But then i thought about performance. Which function is faster? I built my own test following:
<!DOCTYPE HTML>
<html>
<head>
<title>test</title>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
<script type="text/javascript">
function runfirst(dobj,dname){
console.log("runfirst "+dname);
console.time(dname+"-attr");
for(i=0;i<10000;i++){
dobj.attr("data-test","a"+i);
}
console.timeEnd(dname+"-attr");
console.time(dname+"-data");
for(i=0;i<10000;i++){
dobj.data("data-test","a"+i);
}
console.timeEnd(dname+"-data");
}
function runlast(dobj,dname){
console.log("runlast "+dname);
console.time(dname+"-data");
for(i=0;i<10000;i++){
dobj.data("data-test","a"+i);
}
console.timeEnd(dname+"-data");
console.time(dname+"-attr");
for(i=0;i<10000;i++){
dobj.attr("data-test","a"+i);
}
console.timeEnd(dname+"-attr");
}
$().ready(function() {
runfirst($("#rp4"),"#rp4");
runfirst($("#rp3"),"#rp3");
runlast($("#rp2"),"#rp2");
runlast($("#rp1"),"#rp1");
});
</script>
</head>
<body>
<div id="rp1">Testdiv 1</div>
<div id="rp2" data-test="1">Testdiv 2</div>
<div id="rp3">Testdiv 3</div>
<div id="rp4" data-test="1">Testdiv 4</div>
</body>
</html>
It should also show if there is a difference with a predefined data-test or not.
One result was this:
runfirst #rp4
#rp4-attr: 515ms
#rp4-data: 268ms
runfirst #rp3
#rp3-attr: 505ms
#rp3-data: 264ms
runlast #rp2
#rp2-data: 260ms
#rp2-attr: 521ms
runlast #rp1
#rp1-data: 284ms
#rp1-attr: 525ms
So the .attr() function did always need more time than the .data() function. This is an argument for .data() I thought. Because performance is always an argument!
Then I wanted to post my results here with some questions, and in the act of writing I compared with the questions Stack Overflow showed me (similar titles)
And true enough, there was one interesting post about performance
I read it and run their example. And now I am confused! This test showed that .data() is slower then .attr() !?!! Why is that so?
First I thought it is because of a different jQuery library so I edited it and saved the new one. But the result wasn't changing...
So now my questions to you:
Why are there some differences in the performance in these two examples?
Would you prefer to use data- HTML5 attributes instead of data, if it represents a state? Although it wouldn't be needed at the time of coding? Why - Why not?
Now depending on the performance:
Would performance be an argument for you using .attr() instead of data, if it shows that .attr() is better? Although data is meant to be used for .data()?
UPDATE 1:
I did see that without overhead .data() is much faster. Misinterpreted the data :) But I'm more interested in my second question. :)
Would you prefer to use data- HTML5 attributes instead of data, if it
represents a state? Although it wouldn't be needed at the time of
coding? Why - Why not?
Are there some other reasons you can think of, to use .attr() and not .data()? e.g. interoperability? because .data() is jquery style and HTML Attributes can be read by all...
UPDATE 2:
As we see from T.J Crowder's speed test in his answer attr is much faster then data! which is again confusing me :) But please! Performance is an argument, but not the highest! So give answers to my other questions please too!
