Add documentation

Author: hoijnet

lib/woql.js

@@ -310,13 +310,17 @@ WOQL.equals = function (varName, varValue) {
 };
 
 /**
- * Substring
+ * Substring of string
  * @param {string|Var} string - String or variable
  * @param {number|Var} before - integer or variable (characters from start to begin)
  * @param {number|Var} [length] - integer or variable (length of substring)
  * @param {number|Var} [after] - integer or variable (number of characters after substring)
  * @param {string|Var} [substring] - String or variable
  * @returns {WOQLQuery}
+ * @example
+ * let [after, result] = vars("after", "result")
+ * substr("joe", 1, 2, after, result)
+ * //result is "oe", after is 2
  */
 
 WOQL.substr = function (string, before, length, after, substring) {