Saturday, November 23, 2019

How to implement JavaScript for...in loop with examples


Hello guys! morning and welcome to this new tutorial post on JavaScript. In my last tutorial post i talked about JavaScript For Loop, so in this tutorial we are going to be discussing about  another form of looping.

The for....in loop is used to loop through an object's properties. Due to the fact that we have not yet discussed object, you might not feel comfortable with this loop. But once you understand how objects behave in JavaScript, you will appreciate and discover the usefulness of this loop.

You can check out our tutorial post on: JavaScript Operators

Syntax

Below is the syntax of JavaScript for....in loop:

for  (variablename in object)   {
          Statement or block to execute 
}

In each iteration, one property from object is assigned to variablename and this loop continues till all the properties of the object are exhausted.

Example

Try the following example to implement for....in loop. It prints the web browser's Navigator object.

You can also check out our tutorial post on: JavaScript Variables

<html>
     <body>
          <script  type="text/javascript">
               <!--
                    var  aProperty;
                    document.write("Navigator Object Properties <br  />");   
                    for   (aProperty in navigator)  {
                         document.write(aProperty);
                         document.write("<br  />");
                    }
                    document.write("Exiting from the loop! ");
               //-->
          </script>
     </body>
</html>


Below is the output of the above example

Navigator Object Properties 
ServiceWorker
WebkitPersistentStorage
WebkitTemporaryStorage
geolocation 
doNotTrack
onLine
languages 
language 
userAgent 
product 
platform 
appVersion
appName
appCodeName
hardwareConcurrency
maxTouchPoints
vendorSub
vendor 
productSub
CookieEnabled
getStorageUpdates
getGamepads
webkitGetUserMedia
vibrate 
getBattery
sendBeacon
registerProtocolHandler
UnregisterProtocolHandler
Exiting from the loop!

Alright guys we have come to the end of this tutorial post on JavaScript for....in loop.  Follow us on our various social media handles to stay updated. Also feel free to to drop your questions in the comment box below, bye for now.
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