javascript - refactoring working recursion code (hasFiveDIVs) for traversing the DOM -

@oriol provided amazing 2 line recursive solution problem working on today.

function numoccurencesrecursive(arr, val) {   if (!arr.length) return 0;   return (arr[0] === val ? 1 : 0) + numoccurencesrecursive(arr.slice(1), val); } 

i inspired refactor spagetti-ish code wrote yesterday:

//returns boolean     function containsfiveormoredivs(domelement) {       var count = 0;    function docount(domelement) {     if (domelement && domelement.tagname === "div") {       count++;     }      if (count >= 5) {       return true;     }      if (domelement.haschildnodes()) {       var children = domelement.childnodes;       (var = 0; < children.length; i++) {         if (docount(children[i])) {           return true         }       };     };      return false;   }    return docount(domelement) } containsfiveormoredivs(document); 

here's attempt:

function containsfiveormoredivspurerecursion(domelement) {   if (!domelement && domelement.tagname !== "div") {     return 0;   }   return (domelement.tagname === "div" ? 1 : 0) + containsfiveormoredivspurerecursion(domelement.childnodes()); //? } 

how loop through child nodes recursively in version? i'm doing possible?

with recursion, should remember return 1 type of value, want return boolean yet want function return count too. complicates things.

heres recursive function count element types

function countelements(domelement, elementtype) {     count = (domelement && domelement.tagname === elementtype.touppercase());      if (domelement.haschildnodes()) {       (var = 0; < domelement.childnodes.length; i++) {         count += countelements(domelement.childnodes[i], elementtype);        };     };      return count; } 

you can use achieve want.

countelements(document, 'div') >= 5 

however, might not efficient way of doing since traverse whole dom tree want stop when you've hit 5 elements.

function containsfiveormoredivspurerecursion(domelement, elementtype) {     var count = 0;      function countelements(domelement, elementtype) {         count += (domelement && domelement.tagname === elementtype.touppercase());          if (count >= 5) return count;          if (domelement.haschildnodes()) {           (var = 0; < domelement.childnodes.length; i++) {             countelements(domelement.childnodes[i], elementtype);            };         };          return count;     }       return countelements(domelement, elementtype) >= 5; } 

in example, need keep variable outside of function (thus it's not pure recursion) keep track of count , able return boolean.