code: function findResource(name, filepath, extList) {
    var candidates = [name, path.join(name, 'index')];
    var baseName = path.basename(name);
    if (baseName && baseName !== '.' && baseName !== '..') {
      candidates.push(path.join(name, baseName));
    }
    var info = null;
  
    candidates.every(function(candidate) {
      info = fis.uri(candidate, filepath);
  
      for (var i = 0, len = extList.length; i < len && !info.file; i++) {
        info = fis.uri(candidate + extList[i], filepath);
      }
  
      if (info && info.file) {
        return false;
      }
  
      return true;
    });
  
    return info;
  }
docs: 当 require 没有指定后缀时，用来根据后缀查找模块定义。