code: function () {
              var value = this.value;
              var options = this.engine.options;
  
              if (!value
                  || (options.strip && /^\s*$/.test(value))
              ) {
                  return '';
              }
  
              return compileVariable(value, this.engine, 1);
          }
docs: 获取renderer body的生成代码
  
  @return {string} 生成代码