instanceof

javascript有 5种基础的内建对象(Fundamental Objects) ， Object 、 Function 、 Error 、 Symbol 、 Boolean ，而 Object / Function 尤为特殊，是定义其他内建对象或者普通对象和方法的基础。 详细的了解 Object 和 Function 对象有助于更好的理解javascript的一些工作原理。 和其他引用类型一样， Object / Function 既是对象，有自己的方法和属性，也是函数，可以作为构造函数。 本文主要讨论以下几个问题： Fucntion.prototype 和普通对象的 prototype 有何区别？ Object.prototype.__proto__ = ？ Object.__proto__ = ? Object 、 Function 的原型对象有何特殊之处？ Function Function的属性 在ES6标准中，Function 对象有两个属性： length 值为1，这个属性的特性为 { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: true } ，即不可覆盖，不可被 for...in 遍历，但可以通过 Object.defineProperty 修改它的上面这些特性 prototype

一、new 操作符 + Object 创建对象 1 var person = new Object(); 2 person.name = "lisi"; 3 person.age = 21; 4 person.family = ["lida","lier","wangwu"]; 5 person.say = function(){ 6 alert(this.name); 7 } 二、字面式创建对象 1 var person ={ 2 name: "lisi", 3 age: 21, 4 family: ["lida","lier","wangwu"], 5 say: function(){ 6 alert(this.name); 7 } 8 }; 以上两种方法在使用同一接口创建 多个对象时，会产生大量重复代码，为了解决此问题， 工厂模式被开发。 三、工厂模式 function createPerson(name,age,family) { var o = new Object(); o.name = name; o.age = age; o.family = family; o.say = function(){ alert(this.name); } return o; } var person1 = createPerson("lisi",21,["lida","lier",

Is using the instanceof keyword against the essence of object oriented programming ? I mean is it a bad programming practice? I read somewhere that using instanceof keyword means that the design may not be that good. Any better workaround? Generally speaking yes. It's best to keep all code that depends on being a specific class within that class, and using instanceof generally means that you've put some code outside that class. Look at this very simple example: public class Animal { } public class Dog extends Animal { } public class Cat extends Animal { } public class SomeOtherClass { public

After reading up on (again, should have done this a long time ago) implementing equals and hashcode correctly i came to these conclusions,that works for me: If pre JDK 7 : Prefer using Apache commons equalsbuilder and hashcodebuilder. (or Guava). Their javadocs contain examples of how to use them in good way. If JDK 7++ : Use the new Objects utility class But, If writing for hibernate some special requistes appear (see sources farther down) Amongst them are the recommended usage of instanceof instead of getClass , due to hibernate creating proxys of subclasses that are lazy-loaded. But as i

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: This question already has an answer here: How do you check if a variable is an array in JavaScript? [duplicate] 23 answers I want to check a variable is it array? which is the best method used for this to get better performance. isArray or instanceof 回答1: Big guys (Jquery, underscore) do it like this: isArray = Array.isArray || function(obj) { return Object.prototype.toString.call(obj) == '[object Array]'; }; But these are not the droids you're looking for you actually don't need this at all. Don't "check" your variables - just know them.

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I tried finding the sum of all numbers of a nested array, but I don't get it to work correctly. This is what I tried: function arraySum(i) { sum=0; for(a=0;a<i.length;a++){ if(typeof i[a]=="number"){ sum+=i[a]; }else if(i[a] instanceof Array){ sum+=arraySum(i[a]); } } return sum; } Does somebody know where there is a mistake in it? When you try it out with the array [[1,2,3],4,5], it gets 6 as answer, instead of 15. I don't know why. 回答1: The problem with your code is that the sum and a variables are global, instead of local. Because of this

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I'd like a cleaner way to obtain the following functionality, to catch AError and BError in one block: try { /* something */ } catch( AError, BError $e ) { handler1( $e ) } catch( Exception $e ) { handler2( $e ) } Is there any way to do this? Or do I have to catch them separately? AError and Berror have a shared base class, but they also share it with other types that I'd like to fall through to handler2 , so I can't just catch the base class. 回答1: If you can modify the exceptions, use this answer . If you can't, you could try catching all

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I have multiple root elements and thus, I need to write JAXBElement<BookType> jaxbBookType = objectFactory.createBookType (bookType); JAXBElement<OrderType> jaxbOrderType = objectFactory.createOrderType (orderType); and so on. I don't want to write this piece of code again and again. I am trying to write a method which will return me JAXBElement based on its input. What i am trying to write is public <T> JAXBElement<T> getJaxbElement (Object obj){ if (obj instanceof OrderType){ return objectFactory.createOrderType((OrderType)obj); } } But

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: $PHPWord = new PHPWord(); $section = $PHPWord->createSection(); $table = $section->addTable(); $i = 1; $document = $PHPWord->loadTemplate('/var/sitLims/web/uploads/lmsSyllabus/lmsSyllabus.docx'); $document->setValue('Value1', $course_number); $document->setValue('Value2', $course_name); $document->setValue('Value3', $course_en_name); $document->setValue('Value4', $course_summary); $document->setValue('Value5', $course_purposes); $document->setValue('Value6', $course_content); $document->setValue('Value7', $course_exam); $document->setValue(

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I'm catching this fatal exception when I try to pass an Serializable inside an Intent bundle, and I think is related with the nougat shortcuts that I'm trying to implement. here the exception: 12-16 16:17:32.972 20461-20461/***.****.******.debug E/AndroidRuntime: FATAL EXCEPTION: main Process: ***.****.******.debug, PID: 20461 java.lang.IllegalArgumentException: Bad value in PersistableBundle key=shortcutId value=***.****.******.common.cta.CtaAccountSectionModel@1fb70dc at android.os.PersistableBundle.<init>(PersistableBundle.java:124) at