ShortDOI Bookmarklet

gistfile1.js

javascript:var%20metas=document.getElementsByTagName('meta');var%20a='';for(i=0;i<metas.length;i++){if(metas[i].getAttribute('name')=='citation_doi'){a=metas[i].getAttribute('content')}}if(a){location.href='http://shortdoi.org/'+a}else{a=document.documentElement.innerHTML.match(/doi%20*[:=]%20*10[-/0-9a-z.]\/[-/0-9a-z.]+/mig)||document.documentElement.innerHTML.match(/dx.doi.org\/10[-/0-9a-z.]+/mig);if(a==null){alert('Could%20not%20find%20DOI!')}else{a=a.map(function(x){return%20x.match('10.*')[0]});var%20d=a[0];if(a.length>1){var%20c=new%20Array();for(i%20in%20a){if(c[a[i]]){c[a[i]]++}else{c[a[i]]=1}}var%20m=0;d=null;for(i%20in%20c){if(c[i]>m){m=c[i];d=i}else%20if(c[i]==m){d=null}}}if(d==null){alert('More%20than%20one%20DOI%20found!')}else{location.href='http://shortdoi.org/'+d}}}

uncompressed.js

var metas = document.getElementsByTagName('meta'); 

var a = '';

for (i=0; i<metas.length; i++) { 
	if (metas[i].getAttribute('name') == 'citation_doi') { 
		 a = metas[i].getAttribute('content');
	} 
} 

if (a) {
	location.href='http://shortdoi.org/'+a;	
} else {
	a = document.documentElement.innerHTML.match(/doi *[:=] *10[-/0-9a-z.]\/[-/0-9a-z.]+/mig) || document.documentElement.innerHTML.match(/dx.doi.org\/10[-/0-9a-z.]+/mig);

	if (a==null) {
		alert('Could not find DOI!')
	} else {
		a=a.map(function(x){ 
			return x.match('10.*')[0];}
		);
		
		var d=a[0];
		
		if(a.length>1){
			var c=new Array();
			for(i in a) {
				if(c[a[i]]) {
					c[a[i]]++;
				} else{ 
					c[a[i]]=1;
				}
			}

			var m=0;
			d=null;
			for (i in c) {
				if(c[i]>m)
				{
					m=c[i];
					d=i;
				} else if (c[i]==m) {
					d=null;
				}
			}
		}
		if(d==null){
			alert('More than one DOI found!');
		} else {
			location.href='http://shortdoi.org/'+d;
		}
	}

}

This is wonderful, thanks! I use it frequently. I had noticed it fails to detect DOIs on some pages with valid links, such as ACS journals, e.g.:
http://doi.org/crxxtd
I think the problem is the search for 'dx.doi.org', which is now deprecated. I don't know javascript. I deleted the 'dx.', and the DOI is then detected, but it only captures the prefix. So apparently my edit breaks the script, or something else is weird about the ACS links.