An attempt to get a Luhn implementation as small as possible

picoluhn.js

// Input: a string of digits (w/o the check digit)
// Output: the check digit

// Universal algo - smallest option so far (67 chars after the assignment):
luhn=s=>(10-[...s].reverse().reduce((a,v,i)=>a+v*(i&1?1:2.2)|0,0)%10)%10

// IMEI version (14-digit or any other even-digit input) - smallest option so far (57 chars after the assignment):
luhnImei=s=>(10-[...s].reduce((a,v,i)=>a+v*(i&1?2.2:1)|0,0)%10)%10

// Credit card version (15-digit or any other odd-digit input) - smallest option so far (57 chars after the assignment):
luhnCc=s=>(10-[...s].reduce((a,v,i)=>a+v*(i&1?1:2.2)|0,0)%10)%10