This function loops through all images on the page, and serves the appropriately sized image file from a list in a data attribute.
example link: http://total.maloweb.com/responsive
example html:
<img src="default.png" data-widths="400,600,800,1023" data-srcsuffix="-foo.png">
example javascript:
onload=onresize=function(){
respImg("data-widths","data-srcsuffix")
}
example filenames:
400-foo.png
600-foo.png
800-foo.png
1023-foo.png
| function(x,y, //x:attribute name for widths, y:attribute name for suffix | |
| a,c,d,b,e,f,g){ //placeholders | |
| for(d in f=document.images)if(a=f[d],g=a.getAttribute(x)){ //for every image with a width list | |
| b=g.split(","); //split width list into array | |
| for(c=b.length;c--;) //for every width | |
| if(e=b[0],b[c]<a.offsetWidth){ //set lowest width as default(e), when the loop encounters a width smaller than the image: | |
| e=b[c+1]||b[c];break} //set e to one width higher, or the highest width available | |
| a.src=e+a.getAttribute(y) //set src attribute to the right width | |
| } | |
| } |
| function(x,y,a,c,d,b,e,f,g){for(d in f=document.images)if(a=f[d],g=a.getAttribute(x)){b=g.split(",");for(c=b.length;c--;)if(e=b[0],b[c]<a.offsetWidth){e=b[c+1]||b[c];break}a.src=e+a.getAttribute(y)}} |
| { | |
| "name": "respImg", | |
| "description": "Responsive image loading", | |
| "keywords": [ | |
| "responsive", | |
| "conditional", | |
| "image", | |
| "loading" | |
| ] | |
| } |
| <!DOCTYPE html> | |
| <title>Foo</title> | |
| <a href="http://total.maloweb.com/responsive">click link for example</a> |
Reused e for testing if f[d] is actually image element (instead of testing for d.getAttribute, 160bytes):
function(x,y,d,e,f,g){for(d in f=document.images)d=f[d],e=d.offsetWidth,(e&&d[g='getAttribute'](x)||g).replace(/\d+/g,function(c){+c<e&&(d.src=c+d[g](y),e=0)})}
Now I'm out of ideas how to minimize this further.
@atk your functions don't work, they load the lowest resolution image...
Oh, forgot to tell you that you'll have to reverse the order of resolutions in the data attribute. My fault.
@atk I used your tips to make my function a bit smaller 189bytes
function(x,y,a,c,d,e,f,g){for(d in f=document.images)if(d=f[d],g=d[a="getAttribute"](x)){g=g.split(",");for(c=g.length;c--;)if(e=g[0],g[c]<d.offsetWidth)e=g[c+1]||g[c],c=0;d.src=e+d[a](y)}}
your's still doesn't work if I reverse the widths, it always shows one resolution lower.
OK, will have to look into this later. This will probably require to revert the resolution numbers to the former order. Do I get it right in that case that it should always be the resolution 1 notch above (and not below, like it is now) the current one?
Update: made a mix of both of our codes (168bytes):
function(x,y,d,e,f,g,h){for(d in f=document.images)for(e in h=((d=f[d])[g='getAttribute']&&(d[g](x)||'').split(',')))if(h[e]<d.offsetWidth){d.src=h[e+1]+d[g](y);break}}
Another update: rethought my regex version (161bytes):
function(x,y,d,e,f,g){for(d in f=document.images)d=f[d],e=d.offsetWidth,(e&&d[g='getAttribute'](x)||g).replace(/\d+/g,function(c){c>e&&(d.src=c+d[g](y),e=1/0)})}
Last update (depending on the former one): sneaky abuse of string value comparison (159bytes):
function(x,y,d,e,f,g){for(d in f=document.images)d=f[d],e=d.offsetWidth,(e&&d[g='getAttribute'](x)||g).replace(/\d+/g,function(c){c>e&&(d.src=c+d[g](y),e=g)})}
@atk it doesn't work at all now... it either returns "undefined-suffix.png" or "NaN"
I'll have a look into the problem later.
OK, got this now. Forgot that there was no resolution beyond the last one. 176bytes now:
function(x,y,d,e,f,g,h){for(d in f=document.images)for(e in h=((d=f[d])[g='getAttribute']&&(d[g](x)||'').split(',')))if(h[e]<d.offsetWidth){d.src=(h[e+1]||h[e])+d[g](y);break}}
Currently, I am trying to get rid of split, because it's too long. Not sure if this will work, but it goes around the lines of:
function(x,y,d,e,f,g,h,i){for(d in f=document.images)for(d=f[d],e=d.offsetWidth,h=/d+/g;i<e&&(i=h.exec(e&&d[g='getAttribute'](x)||g)[0]||i););i&&(d.src=i+d[g](y))}
@atk the latest two don't work as well...
I'll have to copy your test page so I could test myself...
Can you drop the prefix and simply use "default.png", "400-default.png" and so on as filenames?
@maettig
Sure?
Just a suggestion. I don't know if this is what you want. Simply write <img src="default.png" data-widths="400,600,800,1023"> and use a.src=e+'-'+a.src instead of a.src=e+a.getAttribute(y).
@maettig
Thats a brilliant idea! I'll implement it when I have the time!
Edit:
I just remembered why I didn't do this.
The browser loads the default automatically.
So to prevent loading a useless image, you have to either put no src attribute, or make the src a data url of a one pixel gif or something.
My idea 136 bytes: (posted from my phone, not tested)
function respImg(s,u,d,l){document.images.map(a=>{d=a.dataset,for(l=d[s].split(',');l.length||a.offsetWidth>w=l.shift();)a.src=w+d[u]})}
Reused variable (163bytes):