Count occurrences of all characters present in s2 . .
let count = new Array ( MAX_CHAR ) ; for ( let i = 0 ; i < count . length ; i ++ ) { count [ i ] = 0 ; } for ( let i = 0 ; i < s2 . length ; i ++ ) count [ s2 [ i ] . charCodeAt ( 0 ) ] ++ ;