code: function jscmd(file, type, line, express, start, offset) {
        var storage;
        switch (type) {
          case 'init':
            storage = [];
            for (var i = 0; i < line.length; i ++) {
              storage[line[i]] = 0;
            }
            var condition = express;
            var source = start;
            storage.condition = condition;
            storage.source = source;
            cov[file] = storage;
            break;
          case 'line':
            storage = cov[file];
            storage[line] ++;
            break;
          case 'cond':
            storage = cov[file];
            storage.condition[line] ++;
            return express;
        }
      }
docs: jsc(file, 'init', lines, condtions)
  jsc(file, 'line', lineNum)
  jsc(file, 'cond', lineNum, expr, start, offset)