var?createAssigner?=?function(keysFunc,?undefinedOnly)?{ ????return?function(obj)?{ ??????var?length?=?arguments.length; ??????if?(length?<?2?||?obj?==?null)?return?obj; ??????for?(var?index?=?1;?index?<?length;?index++)?{ ????????var?source?=?arguments[index], ????????????keys?=?keysFunc(source), ????????????l?=?keys.length;??????//為什么這里要是1=keys.length??這樣寫是個什么意思？ ????????for?(var?i?=?0;?i?<?l;?i++)?{ ??????????var?key?=?keys[i]; ??????????if?(!undefinedOnly?||?obj[key]?===?void?0)?obj[key]?=?source[key]; ????????} ??????} ??????return?obj; ????}; ??};