一、 自顶向下的编程形式

以骨干逻辑为开始,而后向下细分逻辑

function isPalindrome (s) {  const filtereds = _filterNonNumberAndChar(s);  const reverseds = _reverseString(filtereds);  return _equalsIgnoreCase(filtereds, reverseds);}function _filterNonNumberAndChar(s) {  return null}function _reverseString(s) {  return null}function _equalsIgnoreCase(s, t) {  return null}