#recursive function

최대 호출 스택 사이즈

당신은 당신이 만든 자바스크립트 엔진을 어떻게 많이 재귀 호출할 수 있는 지 궁금하지?

많은 재귀 함수 호출은 어떻게?

다음과 같은 함수로 알수 있다.(Ben Alman의 gist에서 영감을 얻었다.)

function computeMaxCallStackSize() { try { return 1 + computeMaxCallStackSize(); } catch (e) { // Call stack overflow return 1; } }

Node.js, Firefox, Chrome 3가지의 결과

Node.js: 11034

Firefox: 50994

Chrome: 10402

이 숫자가 의미하는 것은 무엇일까? Mr. Aleph는 V8엔진은 나에게 pointed out 이다, 재귀 호출의 숫자는 당신이 두개의 수량의 지적을 만들수 있다: stack의 사이즈와 stack frame의 사이즈이다(파라미터와 로컬 변수들이 들어있는).computeMaxCallStackSize()의 로컬 변수를 추가의 의해 latter는 verify이 할수 있다. 그거슨 로우 넘버를 리턴할 것이다.

ECMAScript 6의 Tail 호출 최적화

ECMAScript 6에서는 tail call을 최적화 할 것이다 : 만약 함수 호출이 함수안의 마지막 행동이라면, subroutine call이 아닌 “jump”를 통해 처리 될것이다. 즉 당신이 computeMaxCallStackSize()의 조금 재 작성하는 경우 그것은 ECMAScript 6(strict mode)에서 영원히 실행 될 것이다.

function computeMaxCallStackSize(size) { size = size || 1; return computeMaxCallStackSize(size + 1); }

I've been working on a store front website and a CMS (Content Management System) that I created for a client and I learned the hard way that I should have incorporated some sort of input sanitation (oops!). Long story short, I thought it would best to leave direct HTML input enabled in my CMS to facilitate stuff like lists, line breaks, images, etc (::Face-Palm::). However I was still really noobish and didn't consider what those little &'s and whatnot would do to the actual HTML. Since the client had already entered a lot of data for her products, starting over was not an option. The Solution: Build a PHP script that would recursively replace every instance of the offending character. Please note that I made some changes to the the following script in an effort to clean it up for this post, so there is a slight chance that it could throw an error or have an unexpected result.

//Set variables: $dbName = "myDB"; $find = "&"; $replace = "&"; //Return Tables: $result = mysql_list_tables($dbName) or die(mysql_error()); $num_rows = mysql_num_rows($result); //Iterate over tables: for ($i = 0; $i < $num_rows; $i++) { $table = mysql_tablename($result, $i); //Output table name: echo "Table: ".$table . ":<br/>"; //Return fields: $result2 = mysql_query("select * from $table limit 1"); $numOfCols = mysql_num_fields($result2); //Iterate over fields: for($i2=0; $i2<$numOfCols; $i2++){ $res = mysql_query("select * from $table"); $fieldName = mysql_field_name($res, $i2); //Output field name: echo "    ".$fieldName . "<br/>"; mysql_query("UPDATE $table SET $fieldName = replace($fieldName,'$find','$replace')") or die(mysql_error()); } } //Clean up memory: mysql_free_result($result); mysql_free_result($result2);

Pretty simple huh? Just replace the variables ($dbName, $find, $replace) and include your SQL connection info/credentials in the beginning of the script and you should be good. The DB I used this on wasn't very big, so this might not be practical for larger DBs - if you do use this on a larger DB make sure that you increase PHP's timeout and memory allocation. Also, one could include multiple find/replace in arrays and iterate through those by replacing lines 3 and 4 with:

$find = array("&","<",">"); $replace = array("&","<",">");

And replace line 27 with a foreach loop to iterate through the $find array:

foreach($find as $key => $val){ mysql_query("UPDATE $table SET $fieldName = replace($fieldName,'$find[$key]','$replace[$key]')") or die(mysql_error()); }

I needed a function that would recursively drill down into a directory, returning an array with the directory structure and files.  I also needed the function to filter out directories and files that I didn't want listed (in addition to the parent directory markers).  Oddly enough there wasn't much out there to provide examples of how to do this and some of the code snippet I found were just excessively big and complex, so I made getDirs():