11var letterCombinations = function ( digits ) {
2+ // if digits is empty return []
23if ( digits == "" ) { return [ ] }
4+ // we create all possible strings a digit might correspond to
5+ // digit contains number 2-9 so we keep index 0 and 1 as 0
36let k = [ 0 , 0 , "abc" , "def" , "ghi" , "jkl" , "mno" , "pqrs" , "tuv" , "wxyz" ]
7+ // we convert first digit to number
48let m = Number ( digits [ 0 ] )
9+ // we split the corresponding string to alphabets
10+ // and it will store all output
511let a = k [ m ] . split ( "" )
612let [ p , n ] = [ [ ] , [ ] ]
13+ // we loop over all digits from index 1 to last index
714for ( let i = 1 ; i < digits . length ; i ++ ) {
15+ // p will store all possible alphabets for current digit
816p = k [ digits [ i ] ] . split ( "" )
17+ // n will store all the possible combinations made for that digit
918n = [ ]
19+ // all possible combinations for given digit are are p.length*a.length
1020for ( let j = 0 ; j < p . length * a . length ; j ++ ) {
21+ // Math.floor(j/p.length) this let us stay in range of index 0-a.length-1
22+ // j%p.length this let us stay in range of index 0-p.length-1
23+ // thus going over all possible combination for all given a and p indices
1124n . push ( a [ Math . floor ( j / p . length ) ] + p [ j % p . length ] )
1225}
26+ // we update the array a will all current possiblities
1327a = n
1428}
29+ // we return all possible combinations
1530return a
16- } ;
31+ } ;