"foo" instanceof String //=> false "foo" instanceof Object //=> false true instanceof Boolean //=> false true instanceof Object //=> false false instanceof Boolean //=> false false instanceof Object //=> false  //...

The instanceof keyword in JavaScript can be quite confusing when it is first encountered, as people tend to think that JavaScript is not an object-oriented programming language.   What is it? What problems does it solve? When is it appropriate and...

In my particular case:  callback instanceof Function   or   typeof callback == "function"   does it even matter, what's the difference?  Additional Resource:  JavaScript-Garden typeof vs instanceof...

Is there anyway to detect if a JavaScript object is a regex?  For example, I would like to do something like this:  var t = /^foo(bar)?$/i; alert(typeof t); //I want this to return "regexp"   Is this possible?  Thanks!  EDIT: Thanks for all t...

In some of my own older code, I use the following:  Object.prototype.instanceOf = function( iface ) {  return iface.prototype.isPrototypeOf( this ); };   Then I do (for example)  [].instanceOf( Array )   This works, but it seems the following would d...

I'm writing a simple platform game using javascript and html5.  I'm using javascript in an OO manner.  To get inheritance working i'm using the following;  // http://www.sitepoint.com/blogs/2006/01/17/javascript-inheritance/ function copy...

I'm trying to use some of the more advanced OO features of Javascript, following Doug Crawford's "super constructor" pattern. However, I don't know how to set and get types from my objects using Javascript's native type system...

I have played a little bit with typescript and found this:  class Greeter {   e: number;    p: boolean = true; }  const xxx = new Greeter(); // true console.log(xxx instanceof Greeter); const xxx2: Greeter = { e: 1, p: true }; // <--- 1. why is th...

So I have done some reading on the new.target boolean added in Node 6.x. Here is a simple example of new.target provided on MDN  function Foo() {   if (!new.target) throw "Foo() must be called with new";   console.log("Foo instantiated wi...

I'm reading through the code of the class-validator library and it has the following isInstance method in it:  /**  * Checks if the value is an instance of the specified object.  */ isInstance(object: any, targetTypeConstructor: new (...args: any...