tükörszó

let s = 'fsfsfsffdfsfsdfdfdfgsfsffdfsfsgdf'
f = (i, j) =>
    i >= j ? 0 :
    s[i] === s[j]
        ? f(i+1,j-1)
        : 1 + Math.min(f(i+1,j),f(i,j-1))
console.log(
 f(0,s.length-1)
)