javascript - Using an index to find a position in a matrix -

my title might terrible, can explain want here. first of all, challenging myself specific. if guess i'm trying accomplish, please keep answers on topic asking here, , not overall problem solving.

i have string of 25 generated letters. index of letter via str.indexof(c) , let's index 16. visualize str linear representation of 5x5 table, index of 16 4th row, 2nd column of table.

i'm trying find way find row , column using javascript without looping through this:

var row = 1; var index = str.indexof(c) + 1; while(index > 5) {     index = index - 5;     row++; } 

with above code, if index starts 16, end result row 4, index 2 - want. feels there should way algorithm instead of loop.

any thoughts?

why not use maths?

var index = 16; var columnsperrow = 5; row = parseint(index / columnsperrow) + 1; column = index % columnsperrow + 1;