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The screenshot below shows the highlighted JavaScript object being of type Telerik.Web.UI.Grid.

True Object Type in JavaScript

Question : What would be the right JavaScript code to get the true type of JavaScript object $telerik.radControls[6]? I need to dynamically determine the true type at runtime in JavaScript and then do something based on the true type.

I tried the code below, but typeof always returns object.

if (typeof $telerik.radControls[6] === "Telerik.Web.UI.RadGrid") {
   //do something
} else if(typeof $telerik.radControls[6] === "Telerik.Web.UI.RadSearchBox") {
 //do something
} else if (typeof $telerik.radControls[6] === "Telerik.Web.UI.RadTreeView") {
 //do something
}

UPDATE 1

I tried some suggestions mentioned under comments, but I get not available when I use instanceof as in screen show below.

enter image description here

UPDATE 2

I found an interesting fact when using instanceof to determine the true type of a JavaScript object. The code below will not work always. It will only work if there is already an object of type Telerik.Web.UI.RadGrid i.e. a constructor for the object type we are checking has been called. I got the following error when no object of Telerik.Web.UI.RadGrid had been instantiated.

Uncaught TypeError: Expecting a function in instanceof check, but got undefined

Unsafe Code that will work only if the object type exists

if (x instance of Telerik.Web.UI.RadGrid) {
   //do something
}

However, when I used code like below then it will not throw an error even when no object of Telerik.Web.UI.RaGrid type has been instantiated.

Safe Code that will always work i.e. not throw an error

if (typeof Telerik.Web.UI.RadGrid !== "undefined && x instance of Telerik.Web.UI.RadGrid) {
   //do something
}
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  • 1
    if ($telerik.radControls[6] instanceof Telerik.Web.UI.Grid) {... assuming that Telerik.Web.UI.Grid is the constructor function that holds the prototype of the object. Commented Dec 19, 2015 at 17:18
  • 1
    You will have to check instanceOf Commented Dec 19, 2015 at 17:19
  • 1
    Try $telerik.radControls[6].constructor.name Commented Dec 19, 2015 at 17:28
  • 1
    I had copied and pasted a modified version of your code. It looks like you want RadGrid instead of Grid. So $telerik.radControls[6] instanceof Telerik.Web.UI.RadGrid Commented Dec 19, 2015 at 17:43
  • 1
    @squint, Sorry I don't know how I missed that part and didn't notice that Rad was missing. It works. Can you please post this as answer? Commented Dec 19, 2015 at 17:46

1 Answer 1

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The instanceof operator will give you a boolean result telling you if its left operand, an object, has the .prototype of the right operand, a function, in its prototype chain.

So assuming Telerik.Web.UI.RadGrid is the constructor function, you can do this:

$telerik.radControls[6] instanceof Telerik.Web.UI.RadGrid
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