recursive loop (with pdfs)

gistfile1.js

var arr = [1,2,3,4];

function dumbAddOne(arr) {
  if (arr == []) return [];
  else return ([1 + arr[0]]) + dumbAddOne(arr.slice(1));
}

function findActivty(pdfArr){
  if (pdfArr == []) return [];
  if (/Activity/.test(pdfArr[0])) {
    doStuf();
  }
  else return findActivity(pdfArray.slice(1));
}