replace + split

'{"A":"5","B":"4","C":"3","D":"2"}'.replace(/(?:"[^"]+":)|["{}]/g,'').split(',')
["5", "4", "3", "2"]

split

str = '{"A":"5","B":"4","C":"3","D":"2"}';
str.split(/(?:^\{|",)"[^"]+":"|"\}$/g).slice(1,-1)
["5", "4", "3", "2"]

简化~

str.split(/[{"][^:]+:"|"\}/g).slice(1,-1)
["5", "4", "3", "2"]