Javascript 在Javascript中，如何确定对象属性是否存在且不为空？
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In Javascript, How to determine if an object property exists and is not empty?
提问by Amr
Suppose I have the next javascript object:
假设我有下一个 javascript 对象：
var errors = {
error_1: "Error 1 description",
error_2: "Error 2 description",
error_3: "",
error_4: "Error 4 description"
};
How can I determine if the property error_1exists in the errorsobject and is not empty as well?
如何确定该属性是否error_1存在于errors对象中并且也不为空？
回答by AhmadAssaf
if (errors.hasOwnProperty('error_1') && errors['error_1'] )
if (errors.hasOwnProperty('error_1') && errors['error_1'] )
The method hasOwnPropertycan be used to determine whether an object has the specified property as a direct property of that object.
该方法hasOwnProperty可用于确定对象是否具有作为该对象的直接属性的指定属性。
The errors[key]where keyis a string value checks if the value exists and is not null
在errors[key]这里key是一个字符串值，将检查值存在，并且不为空
to Check if its not empty where it is a string then typeof errors['error_1'] === 'string' && errors['error_1'].lengthwhere you are checking for the length of a string
检查它是否不是空的，它是一个字符串，然后typeof errors['error_1'] === 'string' && errors['error_1'].length你检查字符串的长度
Result:
结果：
if (errors.hasOwnProperty('error_1') && typeof errors['error_1'] === 'string' && errors['error_1'].length)
if (errors.hasOwnProperty('error_1') && typeof errors['error_1'] === 'string' && errors['error_1'].length)
Now, if you are using a library like underscoreyou can use a bunch of utility classes like _.isEmpty_.has(obj,key)and _.isString()
现在，如果您使用像下划线这样的库，您可以使用一堆实用程序类，例如_.isEmpty_.has(obj,key)和_.isString()
回答by Phil
To precisely answer your question (exists and not empty), and assuming you're not referring to empty arrays, you could use
要准确回答您的问题（存在且不为空），并假设您不是指空数组，您可以使用
typeof errors.error_1 === 'string' && errors.error_1.length
回答by Amr
Here is a another good answer I foundand wanted to share (after modification to fit my needs):
这是我找到并想分享的另一个很好的答案（经过修改以满足我的需要）：
if ("property_name" in object_name && object_name.property_name !== undefined){
// code..
}
So if I wanted to apply this on my example, it will look like:
因此，如果我想将其应用到我的示例中，它将如下所示：
if ("error_1" in errors && errors.error_1 !== undefined){
// code..
}
回答by Armen Nersisyan
In order to check whether the object is empty or not use this code.
为了检查对象是否为空，请使用此代码。
if (Object.keys(object_name).length > 0) {
// Your code
}
