functionisEmptyObject(value){returnObject.keys(value).length===0&&value.constructor===Object;} 如下方,返回的是我们期待的结果 isEmptyObject(100)// falseisEmptyObject(true)// falseisEmptyObject([])// false 注意,这些数据会报错 // TypeError: Cannot covert undefined or null ot objectgoodEmptyChe...
JavaScript和Java不一样的地方是,Java中判断是否为空只要判断是否等于null就可以了,可是在JavaScript中却不能这样,因为还存在在这另外的几种情况。 下面看看具体的例子: <html> <head> <meta charset="UTF-8"> <title>JavaScript中为空判断</title> </head> <script type="text/javascript"> function stringDee...
javascript 判断变量 是否为空null,undefined, 空数组,空对象,空Object,字符串是否为空或全由空白字符组成,数字是否为0,布尔是否为false。由于Object没有length用 Object.keys()适用于数组(IE8不支持此属性),对象返回可枚举的实例属性名组成的数组来判断是否为空。 利用逻辑判断中or (||)只要有一项为真则不再计算...
TheObject.fromEntries()transforms a list of key-value pairs into an object. I wrotea bookin which I share everything I know about how to become a better, more efficient programmer. You can use the search field on myHome Pageto filter through all of my articles. ...
Once again, this method will fail on a null or undefined input. 3. JSON.stringify The JSON.stringify method is used to convert a JavaScript object to a JSON string. So we can use it to convert an object to a string, and we can compare the result with {} to check if the given ...
JavaScript常见问题:TypeError: null is not an object的详细内容如下: TypeError: null is not an object 这是在 Safari 中读取属性或调用空对象上的方法时发生的错误。 您可以在 Safari Developer Console 中轻松测试。 有趣的是,在 JavaScript 中, null 和 undefined 是并不同,这就是为什么我们看到的是两个...
constructor === Object; value = null; // null value = undefined; // undefined Perfect, no error is thrown 😁# B. Empty Object Check in Older BrowsersWhat if you need to support older browsers? Heck, who am I kidding! We all know when I say older browsers, I'm referring to ...
Object.keys(obj).length ===0&& obj.constructor ===Object; Note:The constructor check makes sure the passed argument is indeed an object. We could also create a reusable function, if you're using the check multiple times in the project: ...
// Undefined variable let a; if (a == null) { console.log('Null or undefined value!'); } else { console.log(a); } This would check whether a is either null or undefined. Since a is undefined, this results in: Null or undefined value! Though, we don't really know which one...
2.Object.prototype.hasOwnProperty() 方法 在这里,我们可以使用对象实例方法 hasOwnProperty() 来检查对象是否包含特定属性。 虽然Object.prototype.hasOwnProperty() 在 JavaScript 规范中已经存在了相当长的时间,但它有一些缺点。hasOwnProperty() 对于使用 Object.create(null) 创建的对象无法工作,因为它不继承自 ...