I know the spec allows both ' and " as delimiters for attribute values, and I also know it's a good practice to always quote.
However I consider " being the cleaner way, maybe it's just me having grown up with C and C++' syntax.
What is the cleanest way of quoting attribute values and why? Please no subjective answers.
Both are fine, but Double quotes are better (IMHO) as you reduce the risk of dynamic values causing errors. e.g.
<input value='${lastName}'/>
<input value='O'Graddy'/>
^^^^^^^
vs.
<input value="${lastName}"/>
<input value="O'Graddy"/>
There’s a lot of rules to remember if you want to omit quotes around attribute values. It’s probably easiest to just use quotes consistently; it avoids all kinds of problems.
If you’re interested, I did some research on unquoted attribute values in HTML, CSS and JavaScript a while ago, and wrote about it here: http://mathiasbynens.be/notes/unquoted-attribute-values
I’ve also created a tool that will tell you if a value you enter is a valid unquoted attribute value or not: http://mothereffingunquotedattributes.com/#foo%7Cbar
