This question already has answers here: How do I check if an object has a specific property in JavaScript? (30 answers) Closed 8 years ago. Which is the right thing to do? if (myObj[‘key’] == undefined) or if (myObj[‘key’] == null) or if (myObj[‘key’]) 2 Try the JavaScript in operator. if (‘key’ in myObj) And … Read more
var obj = { name: “Simon”, age: “20”, clothing: { style: “simple”, hipster: false } } for(var propt in obj){ console.log(propt + ‘: ‘ + obj[propt]); } How does the variable propt represent the properties of the object? It’s not a built-in method or property. Why does it come up with every property in the … Read more
What’s the best way of checking if an object property in JavaScript is undefined? 50 50
How do I check if a particular key exists in a JavaScript object or array? If a key doesn’t exist, and I try to access it, will it return false? Or throw an error? 2 29 Checking for undefined-ness is not an accurate way of testing whether a key exists. What if the key exists … Read more
This question’s answers are a community effort. Edit existing answers to improve this post. It is not currently accepting new answers or interactions. What is the most efficient way to clone a JavaScript object? I’ve seen obj = eval(uneval(o)); being used, but that’s non-standard and only supported by Firefox. I’ve done things like obj = … Read more
Create a copy constructor: class DummyBean { private String dummy; public DummyBean(DummyBean another) { this.dummy = another.dummy; // you can access } } Every object has also a clone method which can be used to copy the object, but don’t use it. It’s way too easy to create a class and do improper clone method. … Read more
By “undefined object as a parameter”, I assume you mean that you’re looking to write a function that doesn’t specify the type of the object in the function declaration, allowing you to only have one function. This can be done with generics. Instead of: static void func(String str) { System.out.println(“The string is: “+str); } static … Read more
What is the best way to go call a function, given a string with the function’s name in a Python program. For example, let’s say that I have a module foo, and I have a string whose content is “bar”. What is the best way to call foo.bar()? I need to get the return value … Read more
You forgot the .class: if (value.getClass() == Integer.class) { System.out.println(“This is an Integer”); } else if (value.getClass() == String.class) { System.out.println(“This is a String”); } else if (value.getClass() == Float.class) { System.out.println(“This is a Float”); } Note that this kind of code is usually the sign of a poor OO design. Also note that comparing the … Read more
You have two ways to do that, both use the Arrays utility class Implement a Comparator and pass your array along with the comparator to the sort method which take it as second parameter. Implement the Comparable interface in the class your objects are from and pass your array to the sort method which takes only one parameter. Example class Book implements Comparable<Book> { public … Read more
