Javascript 测试（对象 && 对象 !== "null" && object !== "undefined" ）
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Javascript test ( object && object !== "null" && object !== "undefined" )
提问by Nick G.
I seem to be using this test a lot
我似乎经常使用这个测试
if( object && object !== "null" && object !== "undefined" ){
doSomething();
}
on objectsI get back from a service call or from reading cookies (since different browsers return the different values null, undefined, "null", or "undefined").
在objects我从一个服务调用或读取饼干回来（因为不同的浏览器返回不同的值null，undefined，"null"，或"undefined"）。
Is there an easier/more efficient way of doing this check?
有没有更简单/更有效的方法来做这个检查？
回答by aquinas
I don't think you can make that any simpler, but you could certainly refactor that logic into a function:
我认为你不能让它变得更简单，但你当然可以将该逻辑重构为一个函数：
function isRealValue(obj)
{
return obj && obj !== 'null' && obj !== 'undefined';
}
Then, at least your code becomes:
然后，至少您的代码变为：
if (isRealValue(yourObject))
{
doSomething();
}
回答by tuchi35
If you have jQuery, you could use $.isEmptyObject().
如果你有 jQuery，你可以使用$.isEmptyObject().
$.isEmptyObject(null)
$.isEmptyObject(undefined)
var obj = {}
$.isEmptyObject(obj)
All these calls will return true. Hope it helps
所有这些调用都将返回 true。希望能帮助到你
回答by Sean Bradley
if(!!object){
doSomething();
}
回答by scatter
If objectis truthy, we already know that it is not nullor undefined(assuming that the string values are a mistake). I assume that a not nulland not undefinedtest is wanted.
如果object是真的，我们已经知道它不是null或undefined（假设字符串值是错误的）。我假设需要一个 notnull和 notundefined测试。
If so, a simple comparison to nullor undefinedis to compare != null.
如果是这样，与null或的简单比较undefined就是比较!= null。
if( object != null ){
doSomething();
}
The doSomethingfunction will run only if objectis neither nullnor undefined.
doSomething仅当object既不是null也不是 时，该函数才会运行undefined。
回答by Snake Eyes
maybe like this
也许像这样
if (typeof object !== "undefined" || object !== null)
// do something
回答by AndriyFM
Maybe like this:
也许是这样的：
var myObj = {};
var isEmptyObj = !Object.keys(myObj).length;
if(isEmptyObj) {
// true
} else {
回答by Harish Mahajan
The best way to check if an object is empty is by using a utility function like the one below.
检查对象是否为空的最佳方法是使用如下所示的实用程序函数。
create a function
创建一个函数
function isEmpty(obj) {
for(var key in obj) {
if(obj.hasOwnProperty(key))
return false;
}
return true;
}
Use above function following way:-
按照以下方式使用上述功能：-
So if you have an empty object, you can check whether it is empty by using the above function.
所以如果你有一个空对象，你可以使用上面的函数检查它是否为空。
var myObj = {}; // Empty Object
if(isEmpty(myObj)) {
// Object is empty (Would return true in this example)
} else {
// Object is NOT empty
}
回答by lmiguelvargasf
I think you could simplify a bit your logic with the following:
我认为您可以通过以下方式简化您的逻辑：
if (object != null && typeof(object) == "object") {
doSomething();
}
The main problem is that if you just check typeof(object) == "object", it will return trueif objectis nullsince null's type is "object". However, if you first check that object != null, you can be sure you are having something that is neither undefinednor null.
主要的问题是，如果你只是检查typeof(object) == "object"，它会返回trueif objectisnull因为它null的类型是"object"。但是，如果您首先检查object != null，您可以确定您所拥有的东西既不是 也不undefined是null。
回答by Sampath
This should work without any issue.
这应该可以正常工作。
if(object){ // checks for null and undefined
doSomething();
}
