code: function (templates, metadata, callback) {
  
          templates = templates || '';
          metadata = metadata || {};
          callback = callback || function () {};
  
          var error = null;
  
          var runtimeCode = runtime({
              type: this.options.type,
              helpers: this._helpersCode,
              templates: templates
          });
  
  
          runtimeCode = this._setMetadata(runtimeCode, metadata);
  
          if (this.options.output !== false) {
              try {
                  this._fsMkdir(path.dirname(this.runtime));
                  fs.writeFileSync(this.runtime, runtimeCode, this.options.charset);
              } catch (e) {
                  error = e;
              }
  
  
              if (this.options.debug) {
                  this._beautify(this.runtime);
              }
  
              if (!this.options.debug && this.options.minify) {
                  this._minify(this.runtime);
              }
          }
  
          callback.call(this, error, runtimeCode);
      }
docs: 编译运行时