如何判断传过来的JSON数据中,某个字段是否存在,
1.obj["key"] != undefined 这种有缺陷,如果这个key定义了,并且就是很2的赋值为undefined,那么这句就会出问题了。 2.!("key" in obj) 这两种方法就比较好了,推荐使用。 答案原文: Actually, checking for undefined-ness is not an accurate way of testing whether a key exists. What if the key exists but the value is actually undefined? var obj = { key: undefined }; You should instead use the in operator: "key" in obj // true, regardless of the actual value If you want to check if a key doesn't exist, remember to use parenthesis: !("key" in obj) // true if "key" doesn't exist in object Or, if you want to particularly test for properties of the object instance (and not inherited properties), usehasOwnProperty: obj.hasOwnProperty("key") // true |