html - Repeat a function in Javascript with .length -

i have long string.

var string = "this long string." 

i have function download string "path".

downloadfunction{... 'echo "'+string+'" >> '+path;} 

how execute function every 2 letters of string? read somewhere using ".length" not sure how implement in case. not want split string array. download function should split string download 2 letters progressively.

i.e. download string 2 letters @ time.

edit: clarify, string needs downloaded x characters @ time download break if exceeds limit.

here example commented on how this:

var string = 'a really long string \     want split 2 letters @ time';  // needs ceiling rounds on odd numbers // otherwise last letter may left out var iterations = math.ceil(string.length / 2);  (var = 0; < iterations; i++) {      // iterating on half of length want go 2 letters @ time     var j = i*2;      // make new string first letter     var letters = string[j]      // if statement check if there second letter     // if there concat first letter     // otherwise last set of odd length concat `undefined`     if (string[j+1]) { letters += string[j+1]; }      // call function here passing `letters`     downloadfunction{... 'echo "' + letters + '" >> '+path;} }