solanto

// some one-liner functions i wrote and condensed as far as i could :)
// warning! some of these pollute the global namespace!

// palindrome checker - 51 chars - string => boolean
([...s])=>s.reduce((a,v,i)=>a*=s.reverse()[i]==v,1)

// roman numeral generator up to 3999 - 138 chars - integer => string
n=>Object.entries({M:1e3,CM:900,D:500,CD:400,C:100,XC:90,L:50,XL:40,X:10,IX:9,V:5,IV:4,I:1}).map(([k,v])=>(a=n,n%=v,k.repeat(a/v))).join``

// shortest vowel distance - 127 chars - lowercase string => array