Javascript 如何检查javascript对象是否包含空值或其本身为空
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/7936480/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
how to check if a javascript object contains null value or it itself is null
提问by mpang
Say I'm accessing a JavaScript Object called jso in Java and I'm using the following statement to test if it's null
假设我正在访问一个在 Java 中称为 jso 的 JavaScript 对象，并且我正在使用以下语句来测试它是否为空
if (jso == null)
However, this statement seems to return true when jso contains some null values, which is not what I want.
但是，当jso包含一些空值时，此语句似乎返回true，这不是我想要的。
Is there any method that can distinguish between a null JavaScript Object and a JavaScript Object that contains some null values?
是否有任何方法可以区分空 JavaScript 对象和包含一些空值的 JavaScript 对象？
Thanks
谢谢
回答by Kirk Woll
To determine whether the target reference contains a member with a null value, you'll have to write your own function as none exist out of the box to do this for you. One simple approach would be:
要确定目标引用是否包含具有空值的成员，您必须编写自己的函数，因为不存在开箱即用的函数来为您执行此操作。一种简单的方法是：
function hasNull(target) {
for (var member in target) {
if (target[member] == null)
return true;
}
return false;
}
Needless to say, this only goes one level deep, so if one of the members on targetcontains another object with a null value, this will still return false. As an exmaple of usage:
不用说，这只会深入一层，所以如果其中一个成员target包含另一个具有空值的对象，这仍然会返回 false。作为用法示例：
var o = { a: 'a', b: false, c: null };
document.write('Contains null: ' + hasNull(o));
Will print out:
会打印出来：
Contains null: true
包含空值：true
In contrast, the following will print out false:
相反，将打印出以下内容false：
var o = { a: 'a', b: false, c: {} };
document.write('Contains null: ' + hasNull(o));
回答by Samuel Liew
This is just for your reference. Do not upvote.
这仅供您参考。不要点赞。
var jso;
document.writeln(typeof(jso)); // 'undefined'
document.writeln(jso); // value of jso = 'undefined'
jso = null;
document.writeln(typeof(jso)); // null is an 'object'
document.writeln(jso); // value of jso = 'null'
document.writeln(jso == null); // true
document.writeln(jso === null); // true
document.writeln(jso == "null"); // false
回答by Niloct
Try an extra =
尝试一个额外的 =
if (jso === null)
